Optical device with slab waveguide and channel waveguides on substrate

ABSTRACT

An optical device used, for example, in an add/drop multiplexer, a dynamic gain equalizer or a optical power monitor. The optical device includes (a) a substrate; (b) a first slab waveguide formed on the substrate; (c) channel waveguides of differing lengths formed on the substrate, light output from the first slab waveguide being input to the channel waveguides; and (d) a second slab waveguide formed on the substrate, light output from the channel waveguides being input to the second slab waveguide. An end face of the second slab waveguide shares a face with an end face of the substrate. The optical device has low loss characteristics.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to Japanese application2003-026614, filed Feb. 4, 2003, and which is incorporated herein byreference, in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to optical signal processing forthe purpose of performing signal pathway switching and light outputpower adjustment for each wavelength in a WDM (Wavelength DivisionMultiplexing) system. More particularly, it is related to an opticalfunctional device that uses flat light guides to integrate andminiaturize components that are necessary for the adding and dropping ofsignals with specific wavelengths, the adjustment and monitoring oflight output power for each wavelength, and wavelength dispersioncompensation for each wavelength.

[0004] 2. Description of the Related Art

[0005] In recent years, the introduction of WDM systems has beenaggressively advanced in order to accommodate for the increase in datatraffic. These systems are basically point to point systems. However,with large-scale photonic networks in which WDM systems are connected ina mesh, in order to reduce operation costs through efficient operationof the WDM systems, it will be indispensable in the future to have anoptical functional device such as a wavelength selective switchoperating as an OADM (Optical Add/Drop Multiplexing) device. An OADM isused for adding and dropping of light signals with specific wavelengths.It will also be necessary for such an optical functional device toprovide for the adjustment and monitoring of light output power for eachwavelength, and for wavelength dispersion compensation for eachwavelength.

[0006]FIG. 1 is an example of a case in which a wavelength selectiveswitch is used in a WDM system.

[0007] In FIG. 1, wavelength division multiplexed light is propagated inthe direction of station M, station N, and station O, which are givenreference numerals 1000, 1002 and 1004, respectively. An OADM node 1006equipped with a wavelength selective switch 1008 is arranged on stationN.

[0008] In the example of the system shown in FIG. 1, light signalsλ1(a)-λ5(a) corresponding to each wavelength λ1-λ5 are contained in thewavelength division multiplexed light from station m.

[0009] At station N, the adding and dropping of light signals havingrequired wavelengths from among the above optical signals is performed.

[0010] The example in the figure shows a situation in which lightsignals λ2(a) and λ4(a) with wavelengths λ2 and λ4, respectively, areoutput to the Drop port, and light signals λ2(b) and λ4(b) having thesame wavelengths λ2 and λ4, respectively, are added to the Out port inthe direction of the next station, station O.

[0011] More specifically, the wavelength division multiplexed light fromstation M is inputted into the IN port of the wavelength selectiveswitch of station N. The wavelength selective switch outputs therequired light signals λ2(a) and λ4(a) to the Drop port. Meanwhile,added signals λ2(b) and λ4(b) are inputted from the Add port into thewavelength selective switch, and outputted to the OUT port in thedirection of station O. Therefore, the wavelength division multiplexedlight with light signals λ1 (a), λ2(b), λ3(a), λ4(b) and λ5(a) areoutput to station O.

[0012] In this way, the wavelength selective switch in this exampledrops light signals of required wavelengths of the inputted wavelengthdivision multiplexed light, and adds light signals that are differentfrom the dropped light signals but are at the same wavelengths.

[0013]FIG. 2 is a first conventional example of a wavelength selectiveswitch which includes a Micro Electro-Mechanical System (MEMS) 1010having mirrors 1012 and 1014. The wavelength selective switch alsoincludes a lens 1016 and a diffraction grating 1018. Generally, the MEMSis a mechanical optical switch that electrically controls the angles ofthe mirrors.

[0014] In FIG. 2, the wavelength selective switch is a configuration inwhich wavelength-multiplexed collimated light that enters from the INport and the ADD port is branched into each wavelength with thediffraction grating. The MEMS mirrors are in the positions ofconvergence of all of the wavelengths.

[0015] Depending on the angles of the corresponding MEMS mirrors, thelight of each wavelength entering from the IN port either heads for theOUT port or is outputted from the DROP port.

[0016] The light of the same wavelength as the light outputted from theDROP port, which entered from the ADD port, is wavelength-multiplexedwith light that enters from the IN port and heads for the OUT port, andit is outputted from the OUT port.

[0017]FIG. 3 is a second conventional example of a wavelength selectiveswitch configuration using arrayed waveguide gratings (AWG) 1020 and1022, diffraction gratings 1024 and 1026, and MEMS mirrors 1028. FIG. 3also shows optical circulators 1030 and 1031, and lenses 1032, 1033,1034, 1036, 1037 and 1038.

[0018] The wavelength multiplexed light that entered from the INPUT portand the ADD port is branched by the first AWG 1020 and the second AWG1022, respectively, into wavelength groups containing multiplewavelengths. They are further branched into each wavelength within eachwavelength group by the first diffraction grating 1024 and seconddiffraction grating 1026, respectively, and they are directed to theMEMS mirrors corresponding to each wavelength.

[0019] The MEMS mirrors are configured such that the decision to returnsignals of light from the first AWG to the first AWG (state 1) or sendit to the second AWG (state 2) can be switched by changing their tiltingangles.

[0020] With the light path when the MEMS mirrors are in state 1, thesignals of light with appropriate wavelengths that entered from the INport are reflected by the MEMS mirrors, and they are returned to thefirst AWG by way of the first diffraction grating. Therefore, they areincluded in the wavelength division multiplexed light that passesthrough the optical circulator 1030 and is outputted from the PASS port(equivalent to the aforementioned OUT port).

[0021] On the other hand, with the light path when the MEMS mirrors arein state 2, the first AWG and the second AWG are in the opticallyconnected state, and the signals of light with appropriate wavelengthsthat entered from the IN port are included in the wavelength divisionmultiplexed light that passes through the second AWG and the opticalcirculator 1031 by way of the second diffraction grating and areoutputted from the DROP port. Moreover, the signals of light withappropriate wavelengths that were sent from the ADD port are included inthe wavelength division multiplexed light that is outputted from thePASS port by way of the first diffraction grating, the first AWG, andthe optical circulator 1030.

[0022] In this way, the device enables the adding and dropping of lightof specific wavelengths through a wavelength selective switch.

[0023] Here, the wavelength selective switch is comprised of awavelength branching filter that resolves wavelength divisionmultiplexed light into each wavelength, a light switch that switches theroutes of the branched light, and a wavelength combining filter thatcombines into one the light of each wavelength after the routes areswitched.

[0024] Furthermore, filters with the same compositions are generallyused for the wavelength branching filter and the wavelength combiningfilter, so this wavelength branching filter and wavelength combiningfilter are hereafter called the wavelength combining/branching filters.

[0025]FIG. 4 is a third conventional example of a wavelength selectiveswitch.

[0026] Here, the device illustrated in FIG. 4 is a wavelength selectiveswitch comprised of light guides, and in the explanations below, devicesof this type are called waveguide type wavelength selective switches. Incontrast to this, wavelength selective switches comprised of diffractiongratings, lenses, MEMS mirrors, etc., as shown in FIG. 2, are calledspatial-join type wavelength selective switches.

[0027] The waveguide type wavelength selective switch of FIG. 4 usesAWGs for wavelength branching filter 1 a and wavelength multiplexingfilter 1 b, and it uses a Mach-Zehnder interferometer type waveguideswitch utilizing thermo-optical effects as light switch 2 (this iscalled a thermo-optical effect type waveguide switch hereafter). FIG. 4shows a slab substrate 100, a core 202 and a clad 201 of the device.

[0028] Here, spatial-join type wavelength selective switches such asthat shown in FIG. 2, have characteristics such that, for example, theyuse free-space diffraction gratings as wavelength combining/branchingfilters, they use mechanical switches (such as MEMS) for light routeswitching, and they use free-space optics systems for optical couplingbetween optical functional components.

[0029] On the other hand, waveguide type wavelength selective switchessuch as that shown in FIG. 4, have characteristics such that, forexample, they monolithically integrate component parts comprised of flatlight guides, they use AWGs for wavelength combining/branching filters,they use thermo-photometric effect type waveguide switches for lightroute switching, and they use waveguides for optical coupling betweenoptical functional components.

[0030] With the first conventional example shown in FIG. 2, it isdifficult to achieve high resolution and miniaturization, which arerequired in WDM systems.

[0031] In order to increase the resolution with diffraction gratings, itis necessary to increase the diameter of the beams that enter thediffraction gratings, and the device consequently grows in size. Theresolution of the diffraction gratings is represented by Nm (N: numberof gratings in the beam irradiation region; m: diffraction order).Assuming the angle of incidence to a diffraction grating is vertical andthe angle of reflection is E from the normal line of the primary surfaceof the diffraction grating, the resolution λ/dλ of the diffractiongrating is expressed by the following Formula (1).

λ/dλ=Nm=N(a*sinθ/λ)  Formula (1)

[0032] Here, a is the interval between grid lines of the diffractiongrating, and A is the wavelength of the light.

[0033] Here, when θ=15° and λ=1.55 μm, the following Formula (2) isapplied.

λ/dλ=Na/5.99 μm  Formula (2)

[0034] Here, if the spacing between reflection mirrors is set to μm=500μm and the beam diameters at the mirror reflection surfaces are set toDm=100 μm, in order to accommodate for a WDM system in which the lightwavelengths are in the spectrum of 1.55 μm and the wavelength intervalsare 0.8 nm with the configuration of the first conventional example,resolution of:

λ/dλ=1.55 μm/0.8 nm×pm/Dm≈10,000  Formula (3)

[0035] becomes necessary. Using Formula (2), the beam diameters Dg atthe diffraction gratings become large, as expressed by:

Dg=Na=λ/dλ×5.99 μm≈6 cm.

[0036] Therefore, the widths of the combining/branching filters withinthe device must be at least 6 cm, causing the entire wavelengthselective switch to require an even broader width.

[0037] As illustrated in FIG. 4, the waveguide type wavelength selectiveswitch is formed on a slab substrate, so it is thin. Because a slabsubstrate with a thickness of approximately 1 mm is normally used, thechip itself is extremely thin. Therefore, it is possible to narrow thethickness of the entire device after it is housed in a protective case.In contrast to this, as stated previously, it is difficult to make thinthe diffraction gratings and lenses used in spatial join type wavelengthselective switches, so there is the problem in which the thickness ofthe entire device becomes large.

[0038] Moreover, with the spatial join type wavelength selective switch,it is necessary to precisely center and fixate the lens in five axisdirections—the direction of the two axes perpendicular to the opticalaxis, the direction of the optical axis, and the mutually orthogonal twoaxes, yaw and pitch or angles. As for optical parts other than the lens,in addition to the above five axes, it is necessary to precisely centerand fixate the parts in the six axes of the rotation direction.Therefore, there is the problem that assembly is troublesome incomparison to the waveguide type wavelength selective switch.

[0039] This is the same for the lenses and diffraction gratings of thesecond conventional example shown in FIG. 3.

[0040] On the other hand, with the second and third conventionalexamples using AWGs, the AWG parts used as wavelengthcombining/branching filters can be designed to be more compact than thecase of diffraction gratings in the first conventional example.

[0041] Therefore, it is possible to make the wavelength selective switchsmaller than the first conventional example, but the insertion loss ofAWGs with configurations such as that shown in FIG. 4 is approximately 3dB each time a light signal passes through. In the second and thirdconventional examples, light signals of each wavelength pass throughAWGs twice—once at the time of branching and once at the time ofmultiplexing—so the fact that the insertion loss of AWGs becomes aslarge as approximately 6 dB. This high insertion loss is a problem.

[0042] The reason that the insertion loss of AWGs of the configurationused in the second and third conventional examples becomes large will beexplained below.

[0043]FIG. 5 is a block diagram of the conventional AWG.

[0044] In FIG. 5, the conventional AWG is comprised of input waveguide3, input slab waveguide 4, channel waveguide array 5 comprising multiplechannel waveguides, output slab waveguide 6, and multiple output channelwaveguides 610.

[0045] Input waveguide 3 is for the purpose of guiding the input lightfrom waveguide end face 203 to input slab waveguide 4, and input slabwaveguide 4 is for the purpose of distributing the input light tochannel waveguide array 5.

[0046] Input slab waveguide 4 extends in the direction parallel to thepage of FIG. 5, and when light enters input slab waveguide 4 from inputwaveguide 3, it freely expands and propagates without being confined inthe direction parallel to the page of FIG. 5.

[0047] In order for light that has freely propagated through input slabwaveguide 4 in the direction parallel to the page to reach channelwaveguide array 5 and optically couple, the power of the input light isdistributed to all of the channel waveguides that constitute channelwaveguide array 5.

[0048] Channel waveguide array 5 is for the purpose of providing phaseshifts to the light that passes through here, and it is formed such thatthe differences between effective light path lengths of adjacentwaveguides are constant.

[0049] Therefore, when light propagates through channel waveguide array5 to the boundary with output slab waveguide 6 from the boundary withinput slab waveguide 4, phase shifts corresponding to the wavelengths ofthe light within each channel waveguide are generated. This phase shiftcontributes to spectroscopy effects described later.

[0050] Output slab waveguide 6 is for the purpose of freely propagatingand interfering with light outputted from channel waveguide array 5.

[0051] When light of the same phase is outputted from each channelwaveguide constituting channel waveguide array 5, light of a givenwavelength is focused on the boundary of the output slab and thewaveguide positioned vertically in the center in FIG. 5 from amongoutput channel waveguides 610.

[0052] This is because the boundary between channel waveguide array 5and output slab waveguide 6 forms an arc centered on this position inwhich light is focused, and the light leaving each channel waveguideproceeds directly towards the center of this arc—that is, the center ofoutput channel waveguides 610 positioned in the central region of thevertical direction. The wavelength at this time is called the centerwavelength.

[0053] In the case in which the wavelength of light is shorter than thecenter wavelength, the phase of the light outputted from channelwaveguide array 5 proceeds to the bottom of the figure. Focusingattention on the position in which the phases of light outputted fromeach channel waveguide are equal (this is called the equal phase fronthereafter), the further they proceed towards the bottom of the figure,the further to the right they are positioned. This is the state in whichphases are advancing. Therefore, light that is shorter than the centerwavelength is relatively focused at the top.

[0054] Conversely, when the wavelength of light is longer than thecenter wavelength, the phases of the light outputted from the channelwaveguides proceed to the top of the figure. Therefore, they arerelatively focused at the bottom.

[0055] In this way, on lines 611 that connect the boundaries betweenoutput slab waveguide 6 and output channel waveguides 610, spectroscopyand conversion are performed as a continuous spectrum in which the topforms short wavelengths and the bottom forms long wavelengths. Moreover,lines 611 that connect the boundaries between output slab waveguide 6and output channel waveguides 610 form an arc.

[0056] Output channel waveguides 610 are for the purpose of cutting outonly light of a specific wavelength band from the continuous spectrumfocused on arc 611 and guiding it to waveguide end face 204, and theycomprise multiple channel waveguides. As previously stated, if thepositions on arc 611 are different, then the wavelength band of trimmedlight out becomes different.

[0057] The spacing between output channel waveguides 610 on arc 611 isproportionate to the wavelengths of outputted light. Therefore, if theoutput channel waveguides are arranged on arc 611 at equal intervals,then the wavelength intervals of light that is trimmed and outputtedalso become equally spaced. Moreover, by adjusting the spacing betweenthe output channel waveguides, it is possible to adjust the wavelengthspacing of the outputted light.

[0058] Furthermore, the configuration of the aforementioned AWGs and thespectroscopy principles thereof are described in, for example, thedocument, “Meint K. Smit and Cor van Dam, IEEE JOURNAL OF SELECTEDTOPICS IN QUANTUM ELECTRONICS, VOL. 2, pp. 236-250 (1996).”

[0059]FIG. 6 is a drawing explaining the distribution of light intensityat the output channel waveguide parts.

[0060]FIG. 6(a) is an enlarged drawing of part A of FIG. 5, and FIG.6(b) is an enlarged drawing of part B of FIG. 6(a).

[0061] As illustrated in FIG. 6(a), the light that is focused on arc 611has an intensity distribution that is strong in the central region, asshown by 612, for example, and rapidly weakens towards the edges(vertical in the diagram).

[0062] For example, supposing that white light is inputted and the lightintensity distribution shown by 612 is the wavelength λc intensitydistribution, then light with slightly short wavelength (λc−Δλ) andlight with slightly long wavelength (λc+Δλ) result with the sameintensity distributions. In the case in which the incident light iswhite light, the light of this intensity distribution continuously formslines.

[0063] At this time, focusing attention on efficiency of coupling withthe output channel waveguides, light with wavelength λc forms a bondwith highest efficiency due to the fact that the output channelwaveguides and the optical axis are in agreement. In contrast to this,the coupling efficiency of light with a wavelength of λc−Δλ or λc+Δλ isdecreased due to the output channel waveguides and the optical axisbeing misaligned, and the coupling efficiency further diminishes as thewavelength deviates from λc.

[0064] Coupling in this case becomes almost the same as Gauss beamcoupling.

[0065]FIG. 7 shows the loss with respect to wavelength of light that isoutputted from the output channel waveguides at this time. This is agraph of the intensity of light outputted from the output channelwaveguides with wavelength on the horizontal axis and intensity on thevertical axis (this becomes the same as the spectrum outputted fromchannel waveguides), and its shape is Gaussian.

[0066] However, in a communications system, the transmission property inwhich the end is roughly flat (called flat top hereafter) is desired.This is because it is desirable for the loss to be roughly equal, evenif each wavelength that constitutes wavelength division multiplexedlight changes within a given spectrum due to changes in environmentalconditions, for example.

[0067] Here, conventional technology for the purpose of flat-topping thetransmission properties will be explained.

[0068]FIG. 8 is a conventional configuration example for the purpose offlat-topping the transmission properties.

[0069] In FIG. 8, broad part 301 (multimode waveguide part) is formed onthe boundary of input waveguide 3 and input slab waveguide 4, and thisperforms the flat-topping of the spectrum. The light intensitydistribution becomes double peaked (referred to as the “double peakmode” hereafter) at the broad part 301 of the input waveguide.

[0070]FIG. 9 is a diagram that describes the light intensitydistribution at the output channel waveguide parts corresponding to FIG.8. FIG. 9(a) is an enlarged drawing of part A of FIG. 8, and FIG. 9(b)is an enlarged drawing of part B of FIG. 9(a).

[0071] When light that moves into the input slab waveguide enters thedouble peak mode, the intensity distribution 612 of light that isfocused on output channel waveguides 610 also enters the double peakmode, as illustrated in FIG. 9(a). In other words, the shape of theintensity distribution of light that moves into the input slab waveguideand the shape of the intensity distribution of light that is focused onoutput channel waveguides 610 are the same.

[0072]FIG. 9(b) shows the intensity distributions of light withwavelength Ac, light with slightly short wavelength (λc−Δλ), and lightwith slightly long wavelength (λc+Δλ). They all form the same shape whenthe incident light is white light.

[0073] The coupling efficiency of this double-peak mode light havingwavelengths λc, λc−Δλ, and λc+Δλ with the output channel waveguidesbecomes constant if the size of the central cavity and the spacingbetween the two peaks are adjusted.

[0074]FIG. 10 is a figure showing the loss with respect to wavelength oflight that is outputted from the output channel waveguides when thespacing between the two peaks is adjusted in this way. As illustrated bythe curve (b) of FIG. 10, for example, flattop transmission propertiesare obtained. Moreover, the curve (a) of FIG. 10 has the Gaussiantransmission properties shown in FIG. 7.

[0075] In this way, by using the structure illustrated in FIG. 8—thatis, by forming part 301 that makes the input waveguide into multiplemode—it is possible to achieve flattop type transmission properties.

[0076] However, as is clear from the comparison of (a) and (b) in FIG.10, the loss in the case of (b)—in which part 301 that makes the inputwaveguide into multiple mode—is greater than that of (a).

[0077] This loss is approximately 3 dB in cases in which light passesthrough AWGs once. In the example of FIG. 3, for example, it passesthrough the AWGs twice, so this results in a loss increase ofapproximately 6 dB.

SUMMARY OF THE INVENTION

[0078] The present invention was conceived with consideration of suchproblems, and its purpose is to provide a compact optical functionaldevice that has flattop type transmission properties and has littleloss.

[0079] Additional objects and advantages of the invention will be setforth in part in the description which follows, and, in part, will beobvious from the description, or may be learned by practice of theinvention.

[0080] Objects of the present invention are achieved by providing anapparatus including (a) a substrate; (b) a first slab waveguide formedon the substrate; (c) channel waveguides of differing lengths formed onthe substrate, light output from the first slab waveguide being input tothe channel waveguides; and (d) a second slab waveguide formed on thesubstrate, light output from the channel waveguides being input to thesecond slab waveguide. An end face of the second slab waveguide shares aface with an end face of the substrate.

[0081] Objects of the present invention are also achieved by providingan apparatus including (a) a substrate; (b) a slab waveguide formed onthe substrate; and (c) channel waveguides of differing lengths formed onthe substrate, light input to the slab waveguide traveling through theslab waveguide and then being input to the channel waveguides. Awavelength division multiplexed (WDM) light is input to the slabwaveguide to thereby travel through the slab waveguide and be input tothe channel waveguides of differing lengths. The channel waveguides ofdiffering lengths have differences in optical path lengths,respectively, so that light at different wavelengths in the WDM light isangularly dispersed from an end face of the substrate in differentdirections, respectively, in accordance with wavelength. The apparatusalso includes a focusing device focusing the angularly dispersed lightsat different wavelengths at different positions, respectively.

[0082] Moreover, objects of the present invention are achieved byproviding an apparatus including a first optical device and a secondoptical device. The first optical device receives a first wavelengthdivision multiplexed (WDM) light, and includes (a) a substrate, (b) aslab waveguide formed on the substrate, and (c) channel waveguides ofdiffering lengths formed on the substrate, wherein the first WDM lightis input to the slab waveguide to thereby travel through the slabwaveguide and be input to the channel waveguides of differing lengths.The channel waveguides of differing lengths have differences in opticalpath lengths, respectively, so that lights at different wavelengths inthe first WDM light are angularly dispersed from an end face of thesubstrate in different directions, respectively, in accordance withwavelength. The second optical device receives a second WDM light, andincludes (a) a substrate, (b) a slab waveguide formed on the substrate,and (c) channel waveguides of differing lengths formed on the substrate,wherein the second WDM light is input to the slab waveguide to therebytravel through the slab waveguide and be input to the channel waveguidesof differing lengths. The channel waveguides of differing lengths havedifferences in optical path lengths, respectively, so that lights atdifferent wavelengths in the second WDM light are angularly dispersedfrom an end face of the substrate in different directions, respectively,in accordance with wavelength. The apparatus also includes at least onefocusing device focusing the lights at different wavelengths angularlydispersed from the first optical device at different positions,respectively, and focusing the lights at different wavelengths angularlydispersed from the second optical device at different positions,respectively, so that angularly dispersed light from the first opticaldevice and angularly dispersed light from the second optical device atthe same wavelength are focused at the same position. A reflector ispositioned at this same position and is controllable to reflect lightfocused at this same position to the first or second optical devices.

[0083] Objects of the present invention are achieved by providing anapparatus including first and second optical devices. The first opticaldevice receives a first wavelength division multiplexed (WDM) light, andincludes (a) a substrate, (b) a first slab waveguide formed on thesubstrate, (c) channel waveguides formed on the substrate, light outputfrom the first slab waveguide being input to the channel waveguides, and(d) a second slab waveguide formed on the substrate, light output fromthe channel waveguides being input to the second slab waveguide. An endface of the second slab waveguide shares a face with an end face of thesubstrate. The first WDM light is input to the first slab waveguide tothereby travel through the first slab waveguide and thereafter be inputto the channel waveguides and then to the second slab waveguide. Thechannel waveguides have differences in optical path lengths,respectively, so that angular dispersion is generated in lights outputfrom the channel waveguides in accordance with wavelengths in the firstWDM light. The second optical device receives a second WDM light, andincludes (a) a substrate, (b) a first slab waveguide formed on thesubstrate, (c) channel waveguides formed on the substrate, light outputfrom the first slab waveguide being input to the channel waveguides, and(d) a second slab waveguide formed on the substrate, light output fromthe channel waveguides being input to the second slab waveguide. An endface of the second slab waveguide shares a face with an end face of thesubstrate. The second WDM light is input to the first slab waveguide tothereby travel through the first slab waveguide and thereafter be inputto the channel waveguides and then to the second slab waveguide. Thechannel waveguides have differences in optical path lengths,respectively, so that angular dispersion is generated in lights outputfrom the channel waveguides in accordance with wavelengths in the secondWDM light. The apparatus includes at least one focusing device focusinglights at different wavelengths angularly dispersed from the firstoptical device at different positions, respectively, and focusing lightsat different wavelengths angularly dispersed from the second opticaldevice at different positions, respectively, so that angularly dispersedlight from the first optical device and angularly dispersed light fromthe second optical device at the same wavelength are focused at the sameposition. The apparatus also includes a reflector positioned at thissame position and controllable to reflect light focused at this sameposition to the first or second optical devices.

[0084] Objects of the present invention are achieved by an apparatusincluding (a) a substrate; (b) a slab waveguide formed on the substrate;and (c) channel waveguides of differing lengths formed on the substrate.Light input to the slab waveguide travels through the slab waveguide andthen is input to the channel waveguides. Subsequent channel waveguideschanneling light of different wavelength bands, respectively, are notformed on the substrate.

[0085] Objects of the present invention are achieved by providing anapparatus including (a) a substrate; (b) a slab waveguide formed on thesubstrate; and (c) channel waveguides of differing lengths formed on thesubstrate. Light output from the slab waveguide is input to the channelwaveguides. Light output from the channel waveguides eventually passesan end face of the substrate, there being no channel waveguides forcutting light of specific wavelength bands, respectively, on thesubstrate through which the light travels between the channel waveguidesof differing lengths and the end face.

[0086] Further, objects of the present invention are achieved byproviding an apparatus including (a) a substrate; (b) a first slabwaveguide formed on the substrate; (c) channel waveguides of differinglengths formed on the substrate, light output from the first slabwaveguide being input to the channel waveguides; and (d) a second slabwaveguide formed on the substrate, light output from the channelwaveguides being input to the second slab waveguide. An end face of thesecond slab waveguide shares a face with an end face of the substrate.

[0087] Objects of the present invention are also achieved by providingan apparatus including (a) a substrate; (b) a first slab waveguideformed on the substrate; (c) channel waveguides of differing lengthsformed on the substrate, light output from the first slab waveguidebeing input to the channel waveguides; and (d) a second slab waveguideformed on the substrate, light output from the channel waveguides beinginput to the second slab waveguide. Light output from the second slabwaveguide eventually passes an end face of the substrate, there being nochannel waveguides for cutting light of specific wavelength bands,respectively, on the substrate through which the light travels betweenthe second slab waveguide and the end face.

[0088] Objects of the present invention are further achieved byproviding an apparatus comprising first and second optical devices. Thefirst optical device receives a first wavelength division multiplexed(WDM) light, and includes (a) a substrate, (b) a slab waveguide formedon the substrate, and (c) channel waveguides of differing lengths formedon the substrate. Subsequent channel waveguides channeling light ofdifferent wavelength bands, respectively, are not formed on thesubstrate. The first WDM light is input to the slab waveguide to therebytravel through the slab waveguide and be input to the channel waveguidesof differing lengths. The channel waveguides of differing lengths havingdifferences in optical path lengths, respectively, so that lights atdifferent wavelengths in the first WDM light are angularly dispersedfrom an end face of the substrate in different directions, respectively,in accordance with wavelength. The second optical device receives asecond WDM light, and includes (a) a substrate, (b) a slab waveguideformed on the substrate, and (c) channel waveguides of differing lengthsformed on the substrate. Subsequent channel waveguides channeling lightof different wavelength bands, respectively, are not formed on thesubstrate. The second WDM light is input to the slab waveguide tothereby travel through the slab waveguide and be input to the channelwaveguides of differing lengths. The channel waveguides of differinglengths have differences in optical path lengths, respectively, so thatlights at different wavelengths in the second WDM light are angularlydispersed from an end face of the substrate in different directions,respectively, in accordance with wavelength. At least one focusingdevice focuses the lights at different wavelengths angularly dispersedfrom the first optical device at different positions, respectively, andfocuses the lights at different wavelengths angularly dispersed from thesecond optical device at different positions, respectively, so thatangularly dispersed light from the first optical device and angularlydispersed light from the second optical device at the same wavelengthare focused at the same position. A reflector is positioned at said sameposition and is controllable to reflect light focused at said sameposition to the first or second optical devices.

[0089] In addition, objects of the present invention are achieved byproviding an apparatus including first and second optical devices. Thefirst optical device receives a first wavelength division multiplexed(WDM) light, and includes (a) a substrate, (b) a slab waveguide formedon the substrate, and (c) channel waveguides of differing lengths formedon the substrate, wherein light output from the channel waveguideseventually passes an end face of the substrate, there being no channelwaveguides for cutting light of specific wavelength bands, respectively,on the substrate through which the light travels between the channelwaveguides of differing lengths and the end face. The first WDM light isinput to the slab waveguide to thereby travel through the slab waveguideand be input to the channel waveguides of differing lengths, the channelwaveguides of differing lengths having differences in optical pathlengths, respectively, so that lights at different wavelengths in thefirst WDM light are angularly dispersed from the end face of thesubstrate in different directions, respectively, in accordance withwavelength. The second optical device receives a second WDM light, andincludes (a) a substrate, (b) a slab waveguide formed on the substrate,and (c) channel waveguides of differing lengths formed on the substrate,wherein light output from the channel waveguides eventually passes anend face of the substrate, there being no channel waveguides for cuttinglight of specific wavelength bands, respectively, on the substratethrough which the light travels between the channel waveguides ofdiffering lengths and the end face. The second WDM light is input to theslab waveguide to thereby travel through the slab waveguide and be inputto the channel waveguides of differing lengths, the channel waveguidesof differing lengths having differences in optical path lengths,respectively, so that lights at different wavelengths in the second WDMlight are angularly dispersed from the end face of the substrate indifferent directions, respectively, in accordance with wavelength. Atleast one focusing device focuses the lights at different wavelengthsangularly dispersed from the first optical device at differentpositions, respectively, and focuses the lights at different wavelengthsangularly dispersed from the second optical device at differentpositions, respectively, so that angularly dispersed light from thefirst optical device and angularly dispersed light from the secondoptical device at the same wavelength are focused at the same position.A reflector is positioned at said same position and is controllable toreflect light focused at said same position to the first or secondoptical devices.

[0090] Objects of the present invention are also achieved by providingan apparatus including first and second optical devices. The firstoptical device receives a first wavelength division multiplexed (WDM)light, and includes (a) a substrate, (b) a first slab waveguide formedon the substrate, (c) channel waveguides formed on the substrate, lightoutput from the first slab waveguide being input to the channelwaveguides, and (d) a second slab waveguide formed on the substrate,light output from the channel waveguides being input to the second slabwaveguide, an end face of the second slab waveguide sharing a face withan end face of the substrate. The first WDM light is input to the firstslab waveguide to thereby travel through the first slab waveguide andthereafter be input to the channel waveguides and then to the secondslab waveguide. The channel waveguides have differences in optical pathlengths, respectively, so that angular dispersion is generated in lightsoutput from the second slab waveguide in accordance with wavelengths inthe first WDM light. The second optical device receives a second WDMlight, and includes (a) a substrate, (b) a first slab waveguide formedon the substrate, (c) channel waveguides formed on the substrate, lightoutput from the first slab waveguide being input to the channelwaveguides, and (d) a second slab waveguide formed on the substrate,light output from the channel waveguides being input to the second slabwaveguide, an end face of the second slab waveguide sharing a face withan end face of the substrate. The second WDM light is input to the firstslab waveguide to thereby travel through the first slab waveguide andthereafter be input to the channel waveguides and then to the secondslab waveguide. The channel waveguides have differences in optical pathlengths, respectively, so that angular dispersion is generated in lightsoutput from the second slab waveguide in accordance with wavelengths inthe second WDM light. At least one focusing device focuses lights atdifferent wavelengths angularly dispersed from the first optical deviceat different positions, respectively, and focuses lights at differentwavelengths angularly dispersed from the second optical device atdifferent positions, respectively, so that angularly dispersed lightfrom the first optical device and angularly dispersed light from thesecond optical device at the same wavelength are focused at the sameposition. A reflector is positioned at said same position andcontrollable to reflect light focused at said same position to the firstor second optical devices.

[0091] As would be understood from the above, an optical functionaldevice of the present invention assumes a structure having a slabwaveguide having an input terminal and multiple channel waveguides withdifferent lengths into which light from the slab waveguide is inputted.

[0092] Moreover, the optical functional device of the present inventionmay also assume a structure having a first slab waveguide having aninput terminal, a second slab waveguide having an output terminal, andmultiple channel waveguides having differing lengths, in which light isinputted from the first slab waveguide and light is outputted to thesecond slab waveguide.

[0093] Furthermore, the optical functional device of the presentinvention may also assume a structure in which, when the channelwaveguides input wavelength division multiplexed light from the inputterminal, the differences of each optical path length are establishedsuch that angular dispersion is generated according to each wavelengthconstituting the wavelength division multiplexed light.

[0094] Furthermore, the optical functional device of the presentinvention may also assume a structure in which the output terminals ofthe channel waveguides are arranged such that they form a straight line.

[0095] Furthermore, the optical functional device of the presentinvention may also assume a structure in which the boundary between thesecond slab waveguide and the channel waveguides is formed in a straightline.

[0096] Furthermore, the optical functional device of the presentinvention may also assume a structure having (A) an optical focusingdevice that focuses light, having each wavelength generating angulardispersion, into different positions based on the angular dispersiondirections, and (B) a light reflection device in at least one positionin which light of each wavelength generating angular dispersion isnearly focused.

[0097] Furthermore, the optical functional device of the presentinvention may also assume a structure having (A) an optical focusingdevice that focuses light, having each wavelength generating angulardispersion, into different positions based on the angular dispersiondirections, and (B) a light reflection device, in which the positions ofthe reflection surface normal line directions differ, in at least oneposition in which light of each wavelength generating angular dispersionis nearly focused.

[0098] Furthermore, the optical functional device of the presentinvention may also assume a structure having (A) an optical focusingdevice that focuses light, having each wavelength generating angulardispersion, into different positions based on the angular dispersiondirections, and (B) a photoelectric conversion device in at least oneposition in which light of each wavelength generating angular dispersionis nearly focused.

[0099] Furthermore, the optical functional device of the presentinvention may also assume a structure having (A) first opticalfunctional device and second optical functional device each having aslab waveguide having an input terminal and multiple channel waveguideswith differing lengths into which light from the slab waveguide isinputted. The optical functional device also includes an opticalfocusing device that focuses light, having each wavelength generatingangular dispersion with the first optical functional device, intodifferent positions based on the angular dispersion directions, and anoptical focusing device that focuses light, having each wavelengthgenerating angular dispersion with the second optical functional device,into different positions based on the angular dispersion directions.Each of the optical functional devices and an optical focusing devicesis arranged such that (i) the position in which light of a givenfrequency generating angular dispersion with the first opticalfunctional device is focused and (ii) the position in which light of thesame frequency generating angular dispersion with the second opticalfunctional device is focused are in agreement. Moreover, there is alight reflection device in at least one position in which light of thewavelengths is nearly focused.

[0100] Moreover, the optical functional device of the present inventionmay also assume a structure having first optical functional device andsecond optical functional devices each having a first slab waveguidehaving an input terminal, a second slab waveguide having an outputterminal, and multiple channel waveguides having differing lengths, inwhich light is inputted from the first slab waveguide and light isoutputted to the second slab waveguide. An optical focusing devicefocuses light, having each wavelength generating angular dispersion withthe first optical functional device, into different positions based onthe angular dispersion directions. Moreover, an optical focusing devicefocuses light, having each wavelength generating angular dispersion withthe second optical functional device, into different positions based onthe angular dispersion directions. Each of the optical functionaldevices and optical focusing devices is arranged such that (i) theposition in which light of a given frequency generating angulardispersion with the first optical functional device is focused and (ii)the position in which light of the same frequency generating angulardispersion with the second optical functional device is focused are inagreement. A light reflection device is in at least one position inwhich light of the wavelengths is nearly focused.

[0101] Furthermore, the optical functional device of the presentinvention may also assume a structure in which the waveguide parts thatconstitute the first optical functional device and the second opticalfunctional device, respectively, are formed on the same substrate.

[0102] Moreover, in various embodiments of the present invention, theoptical functional device may have a structure in which (a) when thechannel waveguides input wavelength division multiplexed light from theinput terminal, the differences of each optical path length areestablished such that angular dispersion is generated according to eachwavelength constituting the wavelength division multiplexed light, and(b) a reflection surface that focuses light, having each wavelengthgenerating angular dispersion, into different positions based on theangular dispersion directions is established inside the second slabwaveguide. Furthermore, in various embodiments of the present invention,the optical functional device may have a light reflection device in atleast one position in which light of each wavelength generating angulardispersion is nearly focused by the reflection surface inside the secondslab waveguide.

[0103] In addition, in embodiments of the present invention, the opticalfunctional device may assume a structure having a light reflectiondevice, in which the positions of the reflection surface normal linedirections differ, in at least one position in which light of eachwavelength generating angular dispersion is nearly focused by thereflection surface inside the second slab waveguide.

[0104] Furthermore, in various embodiments of the present invention, theoptical functional device may have a structure in which (A) a reflectionsurface that focuses light, having each wavelength generating angulardispersion, into different positions based on the angular dispersiondirections is established inside the second slab waveguide, and (B) aphotoelectric conversion device is established in at least one positionin which light of each wavelength generating angular dispersion isnearly focused.

[0105] Furthermore, in various embodiments of the present invention, theoptical functional device may have a structure including a first opticalfunctional device and a second optical functional device each having afirst slab waveguide having an input terminal, a second slab waveguidehaving an output terminal, and multiple channel waveguides havingdiffering lengths, in which light is inputted from the first slabwaveguide and light is outputted to the second slab waveguide. When thechannel waveguides input wavelength division multiplexed light from theinput terminal, the differences of each optical path length areestablished such that angular dispersion is generated according to eachwavelength constituting the wavelength division multiplexed light. Areflection surface that focuses light, having each wavelength generatingangular dispersion, into different positions based on the angulardispersion directions is established inside the second slab waveguide.Each of the optical functional devices and reflection surfaces arearranged such that (i) the position in which light of a given frequencygenerating angular dispersion with the first optical functional deviceis focused and (ii) the position in which light of the same frequencygenerating angular dispersion with the second optical functional deviceis focused are in agreement. A light reflection device is in at leastone position in which light of the wavelengths is nearly focused.

[0106] Furthermore, in various embodiments of the present invention, thewaveguides that constitute the first optical functional device and thewaveguides that constitute the second optical functional device may beformed on the same substrate.

[0107] Furthermore, groups of optical functional devices of the presentinvention may be a group of optical functional devices comprising anytwo or more of the aforementioned optical functional devices, whereinthe waveguides that constitute each optical functional device may beformed on the same substrate.

[0108] Furthermore, the optical functional device of the presentinvention may also assume a structure having a optical device thatoutputs into a second port the light that was inputted into a firstport, and outputs into a third port the light that was inputted into thesecond port, wherein the second port is connected to the input terminal.For example, the optical device might be a circulator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0109] These and other objects and advantages of the invention willbecome apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

[0110]FIG. 1 (prior art) shows an example in which a wavelengthselective switch is used in a WDM system.

[0111]FIG. 2 (prior art) shows a first conventional example of awavelength selective switch configuration.

[0112]FIG. 3 (prior art) shows a second conventional example of awavelength selective switch configuration.

[0113]FIG. 4 (prior art) shows a third conventional example of awavelength selective switch configuration.

[0114]FIG. 5 (prior art) shows a configuration example of a conventionalAWG.

[0115]FIG. 6 (prior art) explains the intensity distribution of light atthe output waveguide input part corresponding to FIG. 5.

[0116]FIG. 7 (prior art) shows the loss with respect to wavelengths oflight outputted from the output waveguide.

[0117]FIG. 8 (prior art) shows a conventional configuration example forthe purpose of flat-topping transmission properties.

[0118]FIG. 9 (prior art) explains the intensity distribution of light atthe output waveguide input part corresponding to FIG. 8.

[0119]FIG. 10 (prior art) shows the loss with respect to wavelengths oflight outputted from the output waveguide corresponding to FIG. 8.

[0120]FIG. 11 explains the basic operations of the present invention.

[0121]FIG. 12 shows the loss with respect to the wavelengths of lightcorresponding to FIG. 11.

[0122]FIG. 13 explains the optical functional device of Embodiment 1.

[0123]FIG. 14 shows an example of the end face of the wavelengthcombining/branching filter of the present invention.

[0124]FIG. 15 is a plan view of the wavelength selective switch ofEmbodiment 2.

[0125]FIG. 16 is a side view of the wavelength selective switch ofEmbodiment 2.

[0126]FIG. 17 is an enlarged drawing of part A of FIG. 15.

[0127]FIG. 18 shows a mirror array configuration example.

[0128]FIG. 19 is a plan view of the wavelength selective switch ofEmbodiment 3.

[0129]FIG. 20 is a side view of the wavelength selective switch ofEmbodiment 3.

[0130]FIG. 21 is an enlarged drawing of part A of FIG. 19.

[0131]FIG. 22 is a plan view of the wavelength selective switch ofEmbodiment 4.

[0132]FIG. 23 is a side view of the wavelength selective switch ofEmbodiment 4

[0133]FIG. 24 is a plan view of the dynamic gain equalizer (DGEQ) ofEmbodiment 5.

[0134]FIG. 25 is a side view of the DGEQ of Embodiment 5.

[0135]FIG. 26 is a plan view of the wavelength selective switch ofEmbodiment 6.

[0136]FIG. 27 is a side view of the wavelength selective switch ofEmbodiment 6.

[0137]FIG. 28 is a plan view of the wavelength selective switch ofEmbodiment 7.

[0138]FIG. 29 is a side view of the wavelength selective switch ofEmbodiment 7.

[0139]FIG. 30 is a plan view of the DGEQ of Embodiment 8.

[0140]FIG. 31 is a side view of the DGEQ of Embodiment 8

[0141]FIG. 32 is a plan view of the wavelength selective switch ofEmbodiment 9.

[0142]FIG. 33 is a side view of the wavelength selective switch ofEmbodiment 9.

[0143]FIG. 34 is a plan view of the wavelength selective switch ofEmbodiment 10.

[0144]FIG. 35 is a side view of the wavelength selective switch ofEmbodiment 10.

[0145]FIG. 36 shows a configuration example of the DGEQ of Embodiment11.

[0146]FIG. 37 shows a configuration example of the wavelength dispersioncompensation device of Embodiment 12.

[0147]FIG. 38 shows a mirror configuration example.

[0148]FIG. 39 shows a configuration example of the optical power monitor(OPM) of Embodiment 13.

[0149]FIG. 40 shows a configuration example of the wavelength selectiveswitch of Embodiment 14.

[0150]FIG. 41 shows a configuration example of the OPM of Embodiment 15.

[0151]FIG. 42 shows a configuration example of a slab optical system.

[0152]FIG. 43 shows another configuration example of a slab opticalsystem.

[0153]FIG. 44 shows a configuration example of the OPM of Embodiment 16.

[0154]FIG. 45 shows a configuration example of the DGEQ of Embodiment17.

[0155]FIG. 46 shows a configuration example of the DGEQ of Embodiment18.

[0156]FIG. 47 shows a configuration example of the wavelength selectiveswitch of Embodiment 19.

[0157]FIG. 48 shows a configuration example of the optical functionaldevice of Embodiment 20.

[0158]FIG. 49 shows a configuration example of the WDM transmissionsystem of Embodiment 21.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0159] Reference will now be made in detail to the present preferredembodiments of the present invention, examples of which are illustratedin the accompanying drawings, wherein like reference numerals refer tolike elements throughout.

[0160]FIG. 11 explains the basic operation of the present invention. InFIG. 11, combining/branching device 20, which is an optical functionaldevice of the present invention, is comprised of input slab waveguide 4,input waveguide 3 as an input terminal that inputs light into this inputslab waveguide 4, output slab waveguide 6 having an output terminal, andchannel waveguide array 5 comprising multiple channel waveguides withdifferent lengths in which light is inputted from input slab waveguide 4and outputted to output slab waveguide 6. FIG. 11 also shows a mirror801 and a lens 12.

[0161]FIG. 12 is a drawing that shows the loss with respect towavelength of light in the case of an optical device that feeds lightfrom input waveguide 3 in FIG. 11, reflects it with mirror 801, andreturns it once again to the input waveguide, and it results in flattopand low-loss properties, as illustrated by curve (c) of FIG. 12.Moreover, curve (a) of FIG. 12 has the Gaussian transmission propertiesshown in FIG. 10.

[0162] The reason that the transmission properties shown by curve (c) inFIG. 12 can be obtained is because channel waveguides (equivalent to 610in FIG. 8) for the purpose of inputting light of each wavelength andleading it to the output terminal are not established incombining/branching device 20 in FIG. 11.

[0163] As described previously with respect to a conventional structuresuch as that in FIG. 8, the channel waveguides on the output terminalside cut out a portion of the spectrum and guide light with specificwavelengths. When trimming this spectrum, there was the problem that thetransmission properties become Gaussian when loss is made low, andinsertion loss increases when the transmission properties areflat-topped.

[0164] In contrast to this, because channel waveguides on the outputterminal side are not present in the combining/branching device to whichthe present invention is applied, the light outputted from thecombining/branching device has an extremely broad spectrum.

[0165] Mirror 801 is what determines the spectrum in FIG. 11.

[0166] Furthermore, the spectrum of light reflected is proportionate tothe width of mirror 801 (the vertical width on the page surface in FIG.11).

[0167] Moreover, with the mirror, the loss will be low as long as thespot in which light is focused is within the effective portion of themirror. Therefore, flattop and low-loss transmission properties can beobtained, as shown by curve (c) in FIG. 12.

[0168] As stated above, by using the combining/branching device as theoptical functional device of the present invention, the effect in whichflattop and low-loss transmission properties can be obtained isgenerated. Moreover, because it is compact and there are few parts toassemble, it is possible to realize low-loss optical functionaldevices—wavelength combining/branching filters for wavelength selectiveswitches, for example—without troublesome assembly.

[0169] Furthermore, in cases in which another optical device—aphotoelectric converter, for example—is arranged in FIG. 11 in place ofmirror 801, because channel waveguides on the output terminal side arenot present, it is clear that the aforementioned effects are achieved.

[0170] Moreover, in this example embodiment, output slab waveguide 6 isestablished for the purpose of reducing the length errors of eachchannel waveguide in order to restrict nonadjacent crosstalk.

[0171] In other words, in the manufacturing process, when it is cut withthe part of channel waveguide array without establishing output slabwaveguide 6, if there is deviation in the cross sectional angles betweenadjacent channel waveguides, this directly becomes the length variationof the channel waveguides.

[0172] However, by establishing a short output slab waveguide 6, itbecomes unnecessary to cut at the location of channel waveguide array 5,so it is possible to restrict length variation of the channel waveguideswith the precision of the photomask used at the time of core processing.

[0173] Due to such reasons, a configuration in which the configurationof FIG. 11 is equipped with output slab waveguide 6 was used, but evenwith a combining/branching device in which output slab waveguide 6 isnot present and the output terminal of channel waveguide array 5 istaken an used the end face, the effect in which flattop and low-losstransmission properties can be obtained. Moreover, because it is compactand there are few parts to assemble, it is clear that it is possible torealize low-loss optical functional devices—wavelengthcombining/branching filters for wavelength selective switches, forexample—without troublesome assembly.

[0174] Example of Embodiment 1

[0175]FIG. 13 is an example of the optical functional device of thepresent invention, and it is an example of a wavelengthcombining/branching filter configuration. FIG. 13(a) is a plan view ofthe wavelength combining/branching filter, FIG. 13(b) is across-sectional view in which the wavelength combining/branching filteris cut by dotted line A-A of FIG. 13(a), FIG. 13(c) is a cross-sectionalview in which the wavelength combining/branching filter is cut by dottedline B-B of FIG. 13(a), and FIG. 13(d) is a cross-sectional view inwhich the wavelength combining/branching filter is cut by dotted lineC-C of FIG. 13(a).

[0176] As shown in FIG. 13(b), for example, the wavelengthcombining/branching filter of the present invention is comprised of slabsubstrate 100 and light guide 200 that is formed on the primary plane ofslab substrate 100. Here, the “primary plane” of slab substrate 100 isthe surface that makes contact with light guide 200 in slab substrate100 of FIG. 13(b), for example.

[0177] Light guide 200 is comprised of clad 201 and core 202, whoseperimeter is enclosed by clad 201 and has a higher index of refractionthan the clad. However, core 202 is exposed only to waveguide end face203 and waveguide end face 204.

[0178] In FIG. 13(a), the shape of the core (called the core patternhereafter) of light guide 200 that constitutes the wavelengthcombining/branching filter contains input slab waveguide 4, inputwaveguide 3 as an input terminal that inputs light into this input slabwaveguide 4, output slab waveguide 6 having an output terminal, andchannel array 5 comprising multiple channel waveguides with differentlengths in which light is inputted from input slab waveguide 4 and lightis outputted to output slab waveguide 6.

[0179] Moreover, the core pattern of light guide 200 in FIG. 13(a) isembedded within clad 201, but for the sake of convenience, it is shownwith a solid line rather than a dotted line. Layers are shown by solidlines in the following plan views, even if they are layers that areembedded in the same way, but as shown in FIG. 13(b), FIG. 13(c), andFIG. 13(d), core 202 is actually embedded within clad 201.

[0180] Furthermore, core 202 of FIG. 13(b) corresponds to inputwaveguide 3 in FIG. 13(a), core 202 of FIG. 13(c) corresponds to inputslab waveguide 4 of FIG. 13(a), and core 202 of FIG. 13(d) correspondsto output slab waveguide 6 of FIG. 13(a).

[0181] Defining the boundary of input slab waveguide 4 and channelwaveguide array 5 of the wavelength combining/branching filterillustrated in FIG. 13(a) as input apertures 501 of channel waveguidearray 5, input apertures 501 of channel waveguide array 5 are positionedon arc 401 with radius R around connection point 400 of input waveguide3 and input slab waveguide 4.

[0182] Furthermore, connection point 400 of input waveguide 3 and inputslab waveguide 4 is on the Rowland circle constituting arc 401, andboundary 402 with input slab waveguide 4 is a part of this Rowlandcircle. Here, “Rowland circle” is a circle with radius R/2, whose arcpasses through the center of a circle with radius R.

[0183] Moreover, as long as it is on this Rowland circle, it is possibleto arrange input waveguide 3 on positions other than position 400 aswell.

[0184] Furthermore, defining the boundary of channel waveguide array 5and output slab waveguide 6 as output apertures 502 of channel waveguidearray 5, the output apertures 502 of channel waveguide array 5 arearranged in a straight line, as shown in the figure. Boundary 601 of thecore that constitutes output slab waveguide 6, the core that constituteschannel waveguide array 5, and clad 201 is configured in a straightline.

[0185] In addition, the length of channel waveguide array 5 is adjustedsuch that the light path length differences between core pattern inputapertures and output apertures of adjacent channel waveguides areconstant.

[0186] This light path difference is established such that, whenwavelength division multiplexed light is inputted from input waveguide3, which is used as an input terminal, angular dispersion is generatedbased on each wavelength that constitutes this wavelength divisionmultiplexed light.

[0187] Therefore, in the embodiments in FIG. 11 through 13, subsequentchannel waveguides channeling light of different wavelength bands,respectively, are not formed on slab substrate 100 after output slabwaveguide 6. In comparison, FIG. 5 and FIG. 8 show conventionalconfigurations where output channel waveguides 610 channeling light ofdifferent wavelength bands, respectively, are formed on the samesubstrate as an output slab waveguide.

[0188]FIG. 14 shows an example of the end face of the wavelengthcombining/branching filter of the present invention.

[0189]FIG. 14(a) is an example of the configuration of waveguide endface 203 on the input waveguide side, and FIG. 14(b) is an example ofthe configuration of waveguide end face 204 on the output slab waveguideside. The waveguide end faces are formed such that both of them share aface with the end face of slab substrate 100. In general, optical fibersare connected to waveguide end face 203 on the input waveguide side.

[0190] As can be seen from FIG. 14(a) and FIG. 14(b), there are noadditional channel waveguides for cutting or channeling light ofspecific wavelength bands, respectively, on slab substrate 100 betweenchannel array waveguide 5 and waveguide end face 204. By comparison,FIG. 5 and FIG. 8 show a conventional arrangements where output channelwaveguides 610 are on a substrate between a channel array waveguide 5and waveguide end face 204.

[0191] Moreover, in cases in which it is necessary to attenuate thereflected light of the waveguide end faces that returns to the opticalfibers or waveguides, the waveguide end faces may be inclined from avertical surface with respect to the optical fibers or waveguides.

[0192] Next, a concrete configuration of the combining/branching filterof this example of embodiment will be explained. For example, using theCVD (Chemical Vapor Deposition) method, on a silicon substrate with athickness of 1 mm (equivalent to slab substrate 100), silica glass forclad with a thickness of 20 μm and silica glass for the core with athickness of 6 μm are stacked on one another.

[0193] Photoresist is applied to this, and through a photolithographyprocess a photoresist pattern having approximately the same shape as thecore pattern is formed. Next, using the photoresist pattern as a mask,reactive ion etching (RIE) is performed and a core pattern is formed.

[0194] Through this process, only the core patterns of input waveguide3, input slab waveguide 4, channel waveguide array 5, and output slabwaveguide 6 are left behind, and core 202 is removed.

[0195] Next, using the CVD method, for example, silica glass for cladwith a thickness of 20 μm is stacked upon the core pattern. Then,waveguide end faces 203 and 204 are simultaneously formed by cuttingwith a cutting machine (dicing machine) that is used for the cutting ofsemiconductor devices. As described above, the combining/branchingfilter of this example of embodiment is formed.

[0196] The concrete dimensions are, for example, as follows: the widthof input waveguide 3 is 6 μm and the length is 5 mm, the radius R of theboundary between input slab waveguide 4 and channel waveguide array 5 is17 mm, the widths of the channel waveguides that constitute channelwaveguide array 5 are 6 μm, the differences of the effective light pathlengths of adjacent channel waveguides from the input apertures to theoutput apertures are 45 μm, and the spacing of the input apertures andthe output apertures of the core pattern of each channel waveguide is 14μm. All core thicknesses are 6 μm and the core/clad specific refractionindex difference=0.8%.

[0197] Also, other materials such as quartz glass or borosilicate glassmay be used for slab substrate 100.

[0198] Moreover, light guides may be produced with manufacturingprocesses other than the CVD method or with materials other than silicaglass—for example, silica glass materials formed with the FHD (FlameHydrolysis Deposition), or plastic materials formed with a coatingmethod.

[0199] The optical system illustrated in FIG. 11 is constructed with thewavelength combining/branching filter that is configured in this way,and the spectrum measured when light is reflected with mirror 801 isillustrated by curve (c) in FIG. 12.

[0200] In FIG. 11, when the focal length of lens 12 was set to 58 mm andthe width of the reflection surface of mirror 801 was set to 100 μm, thespectrum width in which the loss increases by 0.5 dB from the minimumwas 0.8 nm.

[0201] Moreover, when the width of the reflection surface of mirror 801was set to 50 μm, the spectrum width in which the loss increases by 0.5dB from the minimum was 0.4 nm. The insertion loss at this time was 6dB. Therefore, the loss decreased by ½ in comparison to, for example,the case in which the conventional AWGs illustrated in FIG. 8 are used.

[0202] In this way, through the combining/branching device of thisexample of embodiment, flattop and low-loss properties are obtained.Moreover, because it is compact and there are few parts to assemble, itis possible to realize low-loss optical functional devices—wavelengthcombining/branching filters for wavelength selective switches, forexample—without troublesome assembly.

[0203] Moreover, in this example of embodiment, the concrete numericvalues were given for the dimensions of waveguides and the focal lengthsof optical parts such as lenses, but it is obvious that the effects ofthe present invention can be obtained even when the configuration ofthis example of embodiment is applied without depending on these values.

[0204] Example of Embodiment 2

[0205]FIG. 15 and FIG. 16 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 15 shows a plan view ofa wavelength selective switch that is applied to 40-channel wavelengthdivision multiplexed light with frequency intervals of 100 GHz, and FIG.16 shows the side view thereof.

[0206]FIG. 17 is an enlarged drawing of part A of FIG. 15, and itschematically shows the exit directions of light with each wavelengthwhen light that is wavelength-multiplexed with 100 GHz frequencyintervals (equivalent to wavelength intervals of approximately 0.8 nm inthe 1.5 μm wavelength region) is emitted from channel waveguide array 5.

[0207] In FIG. 15 and FIG. 16, the first combining/branching device 20and the second combining/branching device 21 for 100 GHz frequencyintervals are mounted on thermal conduction fin 10, which is mounted onheater 22.

[0208] These combining/branching devices 20 and 21 have identicalstructures, and they are comprised of input slab waveguide 4, inputwaveguide 3 as an input terminal that inputs light into this input slabwaveguide 4, and channel waveguide array 5 comprising multiple channelwaveguides with different lengths in which light is inputted from inputslab waveguide 4.

[0209] When wavelength multiplexed light of 40 channels with 100 GHzfrequency intervals enters input waveguide 3 of the firstcombining/branching device 20, it freely propagates through input slabwaveguide 4, reaches channel waveguide array 5, and optically couples.Therefore, the power of the input light is distributed to each channelwaveguide that constitutes channel waveguide array 5.

[0210] The light within each channel waveguide that constitutes channelwaveguide array 5 causes phase shifts corresponding to its wavelengthand it is outputted from the output terminal, and due to interference,as shown in FIG. 17, it exits as parallel light in an angular dispersiondirection based on each wavelength.

[0211] Light that is branched into each wavelength by channel waveguidearray 5 in this way is led to cylindrical lens 11, and becomes parallellight with respect to the vertical direction (equivalent to the verticaldirection of the page surface in FIG. 16).

[0212] This is the same for the case in which wavelength-multiplexedlight is sent to the second combining/branching device 21.

[0213] Lens 12 is established as an optical device that (a) focuseslight, having each wavelength generating angular dispersion with thefirst combining/branching device 20, into different positions based onthe angular dispersion directions, and (b) focuses light, having eachwavelength generating angular dispersion with the secondcombining/branching device 21, into different positions based on theangular dispersion directions.

[0214] Furthermore, this lens 12 is arranged such that (a) the positionin which light of a given frequency generating angular dispersion withthe first combining/branching device 20 is focused and (b) the positionin which the light of the same frequency generating angular dispersionwith the second combining/branching device 21 are in agreement.

[0215] Moreover, mirror array 13 comprising multiple mirrors is arrangedas a light reflection device that is established in at least oneposition in which light of each frequency generating this angulardispersion is nearly focused, and light of each frequency branched bythe first combining/branching device is fed into this array.

[0216] Mirrors corresponding to each branched wavelength are arranged onmirror array 13. The angle of each mirror is adjusted as necessary, andlight from the first combining/branching device 20 is either returned tothe first combining/branching device 20 or it is reflected to the secondcombining/branching device 21.

[0217] In other words, regarding light with a wavelength in whichswitching is not performed from among wavelength division multiplexedlight sent to the first combining/branching device 20, the reflectionangle of the mirror in the position corresponding to that wavelength isadjusted such that the light from the first combining/branching device20 returns to the first combining/branching device 20.

[0218] On the other hand, regarding light with a wavelength in whichswitching is performed, the reflection angle of the mirror in theposition corresponding to that wavelength is adjusted such that thelight from the first combining/branching device 20 is led to the secondcombining/branching device 21. At this time, light with the samewavelength from the second combining/branching device 21 is reflectedwith this mirror and led to the first combining/branching device 20.

[0219] In this way, the function of a wavelength selective switch, whichis an optical functional device that can (a) drop light of prescribedwavelength from among wavelength division multiplexed light that enteredthe first combining/branching device 20 and lead it to the secondcombining/branching device 21, and (b) add light with the samewavelength as the dropped wavelength from among wavelength divisionmultiplexed light that entered the second combining/branching device 21and return it to the first combining/branching device 20 as wavelengthdivision multiplexed light, is fulfilled.

[0220] Moreover, the input and output of light is conducted with inputwaveguides 3 of combining/branching device 20 and combining/branchingdevice 21, but as an optical device for the purpose of separating inputlight and output light—for example, an optical device that outputs to asecond port the light that was inputted into the first port and outputsto a third port the light that was inputted into this second port, suchas an optical circulator—may be arranged on the input terminal of inputwaveguide 3 of each combining/branching device. This is the same forother examples of embodiment as well.

[0221] In this way, through this example of embodiment, flattop andlow-loss properties can be obtained. Moreover, because it is compact andthere are few parts to assemble, it is possible to realize wavelengthselective switches as low-loss optical functional devices withouttroublesome assembly.

[0222] Here, as an example, each of the combining/branching devices 20and 21 are created on a silicon substrate using quartz waveguides(specific refraction index difference: 0.8%).

[0223] Moreover, as an example, they are designed such that the inputterminal of input waveguide 3 and the output terminal of channelwaveguide array 5 form 90° angles, and as shown in FIG. 17, they arecreated such that each channel waveguide is aligned in parallel at theoutput terminal.

[0224] In the example of FIG. 15, the number of channel waveguides thatconstitute channel array 5 is approximately 300, and in the example ofFIG. 17, the spacing d between each channel waveguide at the outputterminal of channel waveguide array 5 is 14 μm. At this time, thediffraction angle difference between channels (ch) of diffracted lightemitted from the output terminal on the channel waveguide array 5 sideis 0.0017 rad/ch. The diameter of cylindrical lens 11 is 2 mm, and thefocal length is approximately 10 mm.

[0225] The focal length f of lens 12 is approximately 58.3 mm, and it ismounted at a position that is distanced from the output terminal ofchannel waveguide array 5 by focal length f. Its effective diameter is 9mm.

[0226] Furthermore, mirror array 13 is mounted on the opposite side ascylindrical lens 11 in a position that is distanced from lens 12 byfocal length f.

[0227]FIG. 18 is an example of the configuration of mirror array 13.More specifically, FIG. 18(a) is a plan view and FIG. 18(b) is a sideview as seen from the right side, and N mirrors are aligned from ch1 tochN with a nearly constant pitch P. In this example of embodiment, N is40. Moreover, as illustrated in the side view of FIG. 18(b), each mirrorcan be electrically controlled and tilted. Pitch P of mirrors 801 is 100μm, and the size of reflection surfaces 811 is 50 μm×50 μm.

[0228] In FIG. 16, thicknesses d1 and d2 of the combining/branchingdevice mounted parts of thermal conduction fin 10 are both 1 mm, and thedistance d3 between combining/branching mounted parts is 5 mm.Therefore, the two combining/branching devices 20 and 21 are mounteddistanced by 6 mm in the vertical direction.

[0229] The mirror swing angle α is 0.12 rad when light is returned fromcombining/branching device 20 to combining/branching device 20 and whenlight is guided to combining/branching device 21.

[0230] Moreover, in this example of embodiment, by (a) configuring suchthat wavelength division multiplexed light is inputted intocombining/branching device 20, and light that is branched into eachwavelength is reflected by mirrors corresponding to each wavelengthconstituting mirror array 13 and is guided to combining/branching device21, and (b) adjusting the mirror reflection angles to control thequantity of light guided to combining/branching device 21, it ispossible to independently change the intensity of light of eachwavelength constituting the wavelength division multiplexed light.

[0231] In other words, with the configuration of this example ofembodiment, it is possible to realize a device that dynamically controlsthe light power level of each channel (wavelength) corresponding to40-channel wavelength division multiplexed light with 100 GHz frequencyintervals (hereafter, such a device is called a Dynamic Gain Equalizer,abbreviated DGEQ).

[0232] Moreover, with a DGEQ of this configuration, the input ofwavelength division multiplexed light becomes combining/branching device20 and the output becomes combining/branching device 21, so an opticaldevice (such as an optical circulator, for example) for the purposeseparating the input light and the output light becomes unnecessary.

[0233] Furthermore, in other examples of embodiment of wavelengthselective switches configured using the combining/branching devices ofthe present invention as well, it is obvious that utilization as a DGEQis possible by appropriately adjusting the angles of the mirrorscorresponding to each wavelength.

[0234] Example of Embodiment 3

[0235]FIG. 19 and FIG. 20 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 19 shows a plan view ofa wavelength selective switch that is applied to 40-channel wavelengthdivision multiplexed light with frequency intervals of 100 GHz, and FIG.20 shows the side view thereof.

[0236]FIG. 21 is an enlarged drawing of part A of FIG. 19, and itschematically shows the exit directions of light with each wavelengthwhen light that is wavelength-multiplexed with 100 GHz frequencyintervals (equivalent to wavelength intervals of approximately 0.8 nm inthe 1.5 μm wavelength region) is emitted from output slab waveguide 6.

[0237] This example of embodiment is a configuration that is similar toExample of Embodiment 2, but it differs in that (a) thecombining/branching device is directly mounted on heater 22, withoutestablishing a thermal conduction fin on which to mount thecombining/branching device, and (b) a short output slab waveguide 6having an output terminal is established on the end of channel waveguidearray 5 on the opposite side as input slab waveguide 4.

[0238] Specifically, in FIG. 19 and FIG. 20, a first combining/branchingdevice 20 and second combining/branching device 21 for 100 GHz frequencyintervals are respectively mounted on both sides of heater 22, andheater 22 is supported by brace 16.

[0239] These combining/branching devices 20 and 21 have identicalstructures, and they are comprised of input slab waveguide 4, inputwaveguide 3 as an input terminal that inputs light into this input slabwaveguide 4, output slab waveguide 6 having an output terminal, andchannel waveguide array 5 comprising multiple channel waveguides withdifferent lengths in which light is inputted from input slab waveguide 4and light is outputted to output slab waveguide 6.

[0240] Here, the length of the output slab waveguide in this example ofembodiment is 500 μm.

[0241] In this example of embodiment as well, as with the example ofEmbodiment 2 described above, the function of a wavelength selectiveswitch, which is an optical functional device that can (a) drop light ofprescribed wavelength from among wavelength division multiplexed lightthat entered the first combining/branching device 20 and lead it to thesecond combining/branching device 21, and (b) add light with the samewavelength as the dropped wavelength from among wavelength divisionmultiplexed light that entered the second combining/branching device 21and return it to the first combining/branching device 20 as wavelengthdivision multiplexed light, is fulfilled.

[0242] In this way, through this example of embodiment, flattop andlow-loss transmission properties can be obtained. Moreover, because itis compact and there are few parts to assemble, it is possible torealize wavelength selective switches as low-loss optical functionaldevices without troublesome assembly.

[0243] Furthermore, in this example of embodiment, by directly mountingthe combining/branching devices on the heater, it is possible to realizea wavelength selective switch that has even fewer components thanExample of Embodiment 2, and has thinner wavelength combining/branchingfilter parts.

[0244] Moreover, by establishing output slab waveguide 6, it is possibleto restrict the variation of channel waveguide lengths with theprecision of the photomask used at the time of core processing, and itis also possible to restrict nonadjacent crosstalk.

[0245] Example of Embodiment 4

[0246]FIG. 22 and FIG. 23 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 23 shows a plan view ofa wavelength selective switch that is applied to 40-channel wavelengthdivision multiplexed light with frequency intervals of 100 GHz, and FIG.23 shows the side view thereof.

[0247] This example of embodiment is a configuration that is similar tothe example of Embodiment 3, and it differs in that it is configuredsuch that the input terminal face to input waveguide 3 of light signalsand the output terminal face from output slab waveguide 6 are parallel.

[0248] In this example of embodiment as well, as with the example ofEmbodiment 2 described above, flattop and low-loss properties can beobtained. Moreover, because it is compact and there are few parts toassemble, it is possible to realize wavelength selective switches aslow-loss optical functional devices without troublesome assembly.

[0249] Furthermore, in this example of embodiment, by directly mountingthe combining/branching devices on the heater, it is possible to realizea wavelength selective switch that has even fewer components than theexample of Embodiment 2, and has thinner wavelength combining/branchingfilter parts.

[0250] Moreover, by establishing output slab waveguide 6, it is possibleto restrict the variation of channel waveguide length with the precisionof the photomask used at the time of core processing, and it is alsopossible to restrict nonadjacent crosstalk.

[0251] Example of Embodiment 5

[0252]FIG. 24 and FIG. 25 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 24 shows a plan view ofa wavelength DGEQ that is applied to 40-channel wavelength divisionmultiplexed light with frequency intervals of 100 GHz, and FIG. 25 showsthe side view thereof.

[0253] The DGEQ of this example of embodiment uses only one of thecombining/branching devices from among the components of the wavelengthselective switch of the example of Embodiment 4 described above, and itis configured such that the intensity of light that returns to thecombining/branching device is regulated by changing the angles of themirrors corresponding to each wavelength.

[0254] In FIG. 24 and FIG. 25, combining/branching device 20 for 40channels with 100 GHz frequency intervals is mounted on heater 22.

[0255] This combining/branching device 20 is comprised of input slabwaveguide 4, input waveguide 3 as an input terminal that inputs lightinto this input slab waveguide 4, output slab waveguide 6 having anoutput terminal, and channel waveguide array 5 comprising multiplechannel waveguides with different lengths in which light is inputtedfrom input slab waveguide 4 and light is outputted to output slabwaveguide 6.

[0256] Here, the length of the output slab waveguide in this example ofembodiment is 500 μm.

[0257] When wavelength multiplexed light of 40 channels with 100 GHzfrequency intervals enters input waveguide 3 of combining/branchingdevice 20, it freely propagates through input slab waveguide 4, reacheschannel waveguide array 5, and optically couples. Therefore, the powerof the input light is distributed to each channel waveguide thatconstitutes channel waveguide array 5.

[0258] The light within each channel waveguide that constitutes channelwaveguide array 5 causes phase shifts corresponding to its wavelengthand it is outputted from the output terminal, and due to interference,it exits as parallel light in an angular dispersion direction based oneach wavelength.

[0259] Light that is branched into each wavelength by channel waveguidearray 5 in this way is led to cylindrical lens 11, and becomes parallellight with respect to the vertical direction (equivalent to the verticaldirection of the page surface in FIG. 25).

[0260] Moreover, lens 12 is established as an optical device thatfocuses light, having each wavelength generating angular dispersion withcombining/branching device 20, into different positions based on theangular dispersion directions.

[0261] Furthermore, mirror array 13 comprising multiple mirrors isarranged as a light reflection device that is established in at leastone position in which light of each frequency generating this angulardispersion is nearly focused, and light of each frequency branched bycombining/branching device 20 is fed into this array.

[0262] As shown in FIG. 18, forty mirrors corresponding to each branchedwavelength are arranged on mirror array 13. Light is reflected withthese mirrors, the angle of each mirror is adjusted as necessary, andall of the light is either returned to the output terminal of outputslab waveguide 6 of combining/branching device 20 along the same lightpath, or the quantity of light that returns to the output terminal ofoutput slab waveguide 6 is reduced. In this way, the quantity of lightto be returned can be adjusted by the angle of the mirror.

[0263] Therefore, by using a mirror for which the angle of thereflection surface can be electrically controlled, for example, withrespect to wavelength division multiplexed light that is fed intocombining/branching device 20, it functions as a DGEQ that is able toindependently and dynamically attenuate the intensity of light of eachwavelength.

[0264] In this way, through this example of embodiment, flattop andlow-loss transmission properties can be obtained. Moreover, because itis compact and there are few parts to assemble, it is possible torealize DGEQs as low-loss optical functional devices without troublesomeassembly.

[0265] Example of Embodiment 6

[0266]FIG. 26 and FIG. 27 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 26 shows a plan view ofa wavelength selective switch that is applied to 40-channel wavelengthdivision multiplexed light with frequency intervals of 100 GHz, and FIG.27 shows the side view thereof.

[0267] This example of embodiment is a configuration that is similar tothe example of Embodiment 2, and it differs in that (a) 45-degree mirror15 is inserted between lens 12 and mirror array 13 as a device forconverting light paths by 90 degrees, and it is configured such that themounting surfaces of combining/branching devices 20 and 21 and themounting surface of mirror array 13 are parallel to one another, and (b)a short output slab waveguide 6 is established on the emitting end partof the combining/branching device.

[0268] In this example of embodiment as well, flattop and low-losstransmission properties can be obtained. Moreover, because it is compactand there are few parts to assemble, it is possible to realizewavelength selective switches as low-loss optical functional deviceswithout troublesome assembly.

[0269] Furthermore, through this example of embodiment, because thelight path between lens 12 and mirror array 13 is changed by 90 degreesby 45-degree mirror 15, it is possible to reduce the dimensions in thelongitudinal direction. Moreover, because it is configured such that themounting surfaces of combining/branching devices 20 and 21 and themounting surface of mirror array 13 are parallel to one another, in FIG.27, for example, it is also possible to efficiently mount heater 22 andmirror array 13 on the same substrate.

[0270] Moreover, by establishing output slab waveguide 6, it is possibleto restrict the variation of channel waveguide lengths with theprecision of the photomask used at the time of core processing, and itis also possible to restrict nonadjacent crosstalk.

[0271] Example of Embodiment 7

[0272]FIG. 28 and FIG. 29 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 28 shows a plan view ofa wavelength selective switch that is applied to 40-channel wavelengthdivision multiplexed light with frequency intervals of 100 GHz, and FIG.29 shows the side view thereof.

[0273] This example of embodiment is a configuration that is similar tothe example of Embodiment 4, and it differs in that 45-degree mirror 15is inserted between lens 12 and mirror array 13 as an element forconverting light paths by 90 degrees, and it is configured such that themounting surfaces of combining/branching devices 20 and 21 and themounting surface of mirror array 13 are parallel to one another.

[0274] In this example of embodiment as well, as with the example ofEmbodiment 4 described previously, flattop and low-loss transmissionproperties can be obtained. Moreover, because it is compact and thereare few parts to assemble, it is possible to realize wavelengthselective switches as low-loss optical functional devices withouttroublesome assembly.

[0275] Furthermore, through this example of embodiment, because thelight path between lens 12 and mirror array 13 is changed by 90 degrees,it is possible to reduce the dimensions in the longitudinal direction.Moreover, because it is configured such that the mounting surfaces ofcombining/branching devices 20 and 21 and the mounting surface of mirrorarray 13 are parallel to one another, in FIG. 27, for example, it isalso possible to efficiently mount heater 22 and mirror array 13 on thesame substrate.

[0276] Moreover, by establishing output slab waveguide 6, it is possibleto restrict the variation of channel waveguide lengths with theprecision of the photomask used at the time of core processing, and itis also possible to restrict nonadjacent crosstalk.

[0277] Example of Embodiment 8

[0278]FIG. 30 and FIG. 31 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 30 shows a plan view ofa DGEQ that is applied to 40-channel wavelength division multiplexedlight with frequency intervals of 100 GHz, and FIG. 31 shows the sideview thereof.

[0279] This example of embodiment is a configuration that is similar tothe example of Embodiment 5, and it differs in that 45-degree mirror 15is inserted between lens 12 and mirror array 13 as an element forconverting light paths by 90 degrees, and it is configured such that themounting surface of combining/branching device 20 and the mountingsurface of mirror array 13 are parallel to one another.

[0280] In this example of embodiment as well, as in the example ofEmbodiment 5 described previously, flattop and low-loss properties canbe obtained. Moreover, because it is compact and there are few parts toassemble, it is possible to realize DGEQs as low-loss optical functionaldevices without troublesome assembly.

[0281] Furthermore, through this example of embodiment, because thelight path between lens 12 and mirror array 13 is changed by 90 degreesby 45-degree mirror 15, it is possible to reduce the dimensions in thelongitudinal direction. Moreover, because it is configured such that themounting surface of combining/branching device 20 and the mountingsurface of mirror array 13 are parallel to one another, in FIG. 31, forexample, it is possible to efficiently mount heater 22 and mirror array13 on the same substrate.

[0282] Moreover, by establishing output slab waveguide 6, it is possibleto restrict the variation of channel waveguide lengths with theprecision of the photomask used at the time of core processing, and itis also possible to restrict nonadjacent crosstalk.

[0283] Example of Embodiment 9

[0284]FIG. 32 and FIG. 33 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 33 shows a plan view ofa frequency selection switch that is applied to 40-channel wavelengthdivision multiplexed light with frequency intervals of 100 GHz, and FIG.33 shows the side view thereof. In FIG. 32 and FIG. 33, opticalcirculators 30 and 31 and filters 32 and 33 are schematicallyrepresented.

[0285] In FIG. 32 and FIG. 33, optical circulators 30 and 31 are anexample of an optical device that outputs to a second port (b) lightthat was inputted to the first port (a), and outputs to a third port (c)light that was inputted to the second port (b).

[0286] In FIG. 32, if 40-channel wavelength division multiplexed lightwith 100 GHz frequency intervals is inputted from port a (IN port) ofoptical circulator 30, then the light reaches filter 32 by way of portb.

[0287] Moreover, if wavelength division multiplexed light comprisinglight of wavelengths added to the wavelength division multiplexed lightdescribed above is inputted from port a (ADD port) of optical circulator31, then the light reaches filter 33 by way of port b.

[0288] Here, filters 32 and 33 are configured such that if 40-channelwavelength division multiplexed light with 100 GHz frequency intervalsis inputted from input/output terminal d, then light from the wavelengthspectrum of the 20 channels on the short wavelength side is outputtedfrom input/output terminal e, and light from the wavelength spectrum ofthe 20 channels on the long wavelength side is outputted frominput/output terminal f. Conversely, if light from the wavelengthspectrum of the 20 channels on the short wavelength side and light fromthe wavelength spectrum of the 20 channels on the long wavelength sideare inputted from input/output terminals e and f, respectively, then thelight from these frequency spectrums combines and is outputted frominput/output terminal d.

[0289] Wavelength division multiplexed light of the 20 channels on theshort wavelength side is guided into wavelength selective switch 40 andbranched into each channel by combining/branching device 20 andcombining/branching device 21 that is mounted below combining/branchingdevice 20, respectively, and it is led to either combining/branchingdevice 20 or combining/branching device 21 according to the angle of themirror corresponding to each wavelength constituting mirror array 13.

[0290] The light of each wavelength that is guided tocombining/branching device 20 and combining/branching device 21 iscombined, and it is outputted to port c of optical circulator 30 (OUTport) and port c of optical circulator 31 (DROP port), respectively, byway of filter 32 and filter 33, respectively.

[0291] On the other hand, wavelength division multiplexed light of the20 channels on the long wavelength side is guided into wavelengthselective switch 41 and branched into each channel bycombining/branching device 24 and combining/branching device 25 that ismounted below combining/branching device 24, respectively, and it is ledto either combining/branching device 24 or combining/branching device 25according to the angle of the mirror corresponding to each wavelengthconstituting mirror array 13.

[0292] The light of each wavelength that is guided tocombining/branching device 24 and combining/branching device 25 iscombined. It is then combined with light that was combined bycombining/branching device 20 and combining/branching device 21described above by way of filter 32 and filter 33, respectively, and itis outputted to port c of optical circulator 30 (OUT port) and port c ofoptical circulator 31 (DROP port), respectively.

[0293] Here, from among the spectrum of 40 channels with 100 GHzfrequency intervals, which is the spectrum of input light, wavelengthselective switch 40 is configured to be applied to wavelength divisionmultiplexed light of the wavelength spectrum of the 20 channels on theshort wavelength side, and wavelength selective switch 41 is configuredto be applied to wavelength division multiplexed light of the wavelengthspectrum of the 20 channels on the long wavelength side. Twenty mirrorscorresponding to each branched wavelength are arranged on mirror array13 of each of the wavelength selective switches.

[0294] In this way, through this example of embodiment, flattop andlow-loss properties can be obtained. Moreover, because it is compact andthere are few parts to assemble, it is possible to realize wavelengthselective switches as low-loss optical functional devices withouttroublesome assembly.

[0295] Furthermore, through this example of embodiment, it is possibleto configure the wavelength selective switch applied to 40 channels with100 GHz frequency intervals as four combining/branching devices appliedto 20 channels with 100 GHz frequency intervals. As for thecombining/branching devices applied to 20 channels with 100 GHzfrequency intervals, because it is possible to use combining/branchingdevices with diffraction orders that are higher than combining/branchingdevices applied to 40 channels with 100 GHz frequency intervals, it ispossible to enlarge the diffraction angles. Furthermore, it is possibleto make the focal distance f of lens 12 short, and miniaturization inthis focal length direction is also possible.

[0296] Here, each of the combining/branching devices that constitutewavelength selective switches 40 and 41 is comprised of input slabwaveguide 4, input waveguide 3 as an input terminal that inputs lightinto this input slab waveguide 4, output slab waveguide 6 having anoutput terminal, and channel waveguide array 5 comprising multiplechannel waveguides with different lengths in which light is inputtedfrom input slab waveguide 4 and light is outputted to output slabwaveguide 6.

[0297] Moreover, the length of the output slab waveguides in thisexample of embodiment is 500 μm.

[0298] The channel waveguide spacing at the output terminal is 14 μm.The diffraction angle difference between channels (100 GHz frequencyintervals) of diffracted light emitted from the output terminal on thechannel waveguide side at this time is 0.0034 rad/ch (diffraction order60).

[0299] The diameter of cylindrical lens 11 is 2 mm, and the focal lengthis approximately 10 mm. The focal length of the convex lens isapproximately 29.2 mm, and it is mounted in a position that is distancedfrom the combining/branching device output terminal by this focallength. The effective diameter of the lens is 9 mm.

[0300] Moreover, in FIG. 32, each combining/branching device is aconfiguration having output slab waveguides, but it is clear that thesame functionality and effects are fulfilled by a configuration in whicha channel waveguide array forms the output terminal rather than outputslab waveguides.

[0301] Example of Embodiment 10

[0302]FIG. 34 and FIG. 35 show an example of embodiment of the opticalfunctional device of the present invention. FIG. 34 shows a plan view ofa frequency selection switch that is applied to 40-channel wavelengthdivision multiplexed light with frequency intervals of 100 GHz, and FIG.35 shows the side view thereof.

[0303] In FIG. 34, the two combining/branching devices 20 and 21 for40-channel multiplexing with 100 GHz frequency intervals are mounted ina line on the top face of heater 22.

[0304] Each mounted combining/branching device is comprised of inputslab waveguide 4, input waveguide 3 as an input terminal that inputslight into this input slab waveguide 4, output slab waveguide 6 havingan output terminal, and channel waveguide array 5 comprising multiplechannel waveguides with different lengths in which light is inputtedfrom input slab waveguide 4 and light is outputted to output slabwaveguide 6.

[0305] Moreover, the length of the output slab waveguides in thisexample of embodiment is 500 μm.

[0306] Wavelength division multiplexed light is inputted tocombining/branching device 20, light that was branched into eachwavelength is sent to cylindrical lens 11, and the vertical direction ismade into parallel light. This is focused with lens 12 and sent tomirror array 13, which is arranged in the position in which the light isfocused.

[0307] At this time, the light is bent 90 degrees using 45-degree mirror15. Furthermore, the light is bent to the diagonal lower side using oneof the faces of 45-degree mirror 17, which has two reflection surfaces,and it is sent to mirror array 13 that is mounted on the bottom.

[0308] Mirrors 40 are arranged on mirror array 13 corresponding to ateach wavelength at a pitch of 100 μm.

[0309] As necessary, the angle of the reflection surface with respect tothe incident light of the mirror is changed, this is bent in thedirection of 45-degree mirror 18 using a reflection surface of thedouble-faced 45-degree mirror 17 that is different from the surface towhich light was sent from combining/branching device 20, and light ofappropriate wavelengths is bent 90 degrees with this 45-degree mirror 18and sent to combining/branching device 21.

[0310] Alternatively, the angle of the reflection surface with respectto the incident light of the mirror is changed, and light of appropriatewavelengths is returned to combining/branching device 20 using the samelight path as the incident light path.

[0311] Here, each combining/branching device may be created separatelywith the same method as with the example of Embodiment 3 describedpreviously, or two combining/branching devices may be createdsimultaneously on the same slab substrate.

[0312] In this example of embodiment as well, as with the example ofEmbodiment 4 described previously, flattop and low-loss properties canbe obtained. Moreover, because it is compact and there are few parts toassemble, it is possible to realize wavelength selective switches aslow-loss optical functional devices without troublesome assembly.

[0313] Furthermore, through this embodiment, it is possible toefficiently mount combining/branching device 20 and combining/branchingdevice 21 on the same flat surface, and in order to change the lightpath between lens 12 and mirror array 13, it is possible to shorten thedimensions in the lengthwise direction.

[0314] Example of Embodiment 11

[0315]FIG. 36 is an example of embodiment of the optical functionaldevice of the present invention, a DGEQ that can dynamically control thelight power levels of each channel (wavelength) in WDM communications.

[0316] In FIG. 36, the DGEQ of this example of embodiment is equippedwith optical circulator 30 as an optical device that outputs to a secondport (b) light that was inputted to the first port (a), and outputs to athird port (c) light that was inputted to the second port (b).

[0317] Combining/branching device 20 of this example of embodiment iscomprised of input slab waveguide 4, input waveguide 3 as an inputterminal that inputs light into this input slab waveguide 4, output slabwaveguide 6, and channel waveguide array 5 comprising multiple channelwaveguides with different lengths in which light is inputted from inputslab waveguide 4 and light is outputted to output slab waveguide 6.

[0318] If wavelength division multiplexed light is inputted from the INport (port (a)) of optical circulator 30, the input light generatesangular dispersion with combining/branching device 20 and is branchedinto each wavelength. With an optics system that is comprised ofcylindrical lens 803, lens 804 as an optical device for focusing lightof each wavelength generating this angular dispersion into differentpositions based on the angular dispersion directions, and mirrors 805and 806 as a device for changing light paths, the light is focused onmultiple mirrors 801 corresponding to each wavelength (these lightroutes are called forward paths hereafter).

[0319] Here, if the angles of mirrors 801 are adjusted such that thereflection surfaces are nearly perpendicular to the incident light, thenthe light reflected with mirrors 801 when the reflection surfaces areprecisely perpendicular to the incident light is sent back along thesame route as the forward path, and the loss of light outputted from theOUT port of optical circulator 30 (this is called the return path)reaches a minimum. If it deviates from this angle, the intensity oflight outputted from the OUT port of optical circulator 30 by way of thereturn path becomes small as the deviation becomes large.

[0320] In this way, it is possible to realize a device that can controlthe intensity of light of each wavelength that constitutes incidentwavelength division multiplexed light by adjusting the angles of mirrors801— in other words, it is possible to realize a DGEQ.

[0321] Through this example of embodiment, flattop and low-lossproperties can be obtained. Moreover, because it is compact and thereare few parts to assemble, it is possible to realize DGEQs as low-lossoptical functional devices without troublesome assembly.

[0322] The concrete composition of the DGEQ of this example ofembodiment will be explained hereinafter.

[0323] In FIG. 36, after a block (spline) made of, for example,borosilicate glass is adhered to the tip of combining/branching device20, cylindrical lens 803 with a focal length of 10 mm is adhered, andthe vertical direction of the output light is made into parallel light.

[0324] Lens 804 is arranged such that its focal point coincides with theboundary of the core pattern for channel waveguide array 5 and the corepattern for output slab waveguide 6 of combining/branching device 20.The light path is bent with mirrors 805 and 806, and mirror array 13 inwhich multiple mirrors 801 illustrated in FIG. 18 are arranged isestablished at the other focal point of lens 804.

[0325] Optical circulator 30 is connected to the input waveguide 3 sidethrough a block (spline) made of, for example, borosilicate glass andsignal mode fibers that are sandwiched by the borosilicate glass block.

[0326] Moreover, for the sake of convenience in FIG. 36, the light pathsof light of three branched wavelengths are shown and only three mirrors801 corresponding to these are shown, but it is obvious that the numberof branched wavelengths and the number of mirrors 801 are not limited tothese numbers.

[0327] Example of Embodiment 12

[0328]FIG. 37 is an example embodiment of the optical functional deviceof the present invention as a wavelength dispersion compensation devicein WDM communications.

[0329] The configuration of the wavelength dispersion compensationdevice shown in FIG. 37 is almost the same as the configuration of theDGEQ shown in FIG. 36, and it differs in that each mirror thatconstitutes mirror array 13 is different from those shown in FIG. 18.

[0330] In other words, mirror array 13 shown in FIG. 37 is establishedin at least one position in which light of each wavelength generatingangular dispersion with combining/branching device 20 is nearly focused,and it is arranged as a light reflection device in which the positionsof the reflection surface normal line directions differ.

[0331]FIG. 38 is an example of the configuration of mirrors 821 thatconstitute mirror array 13 in FIG. 37. FIG. 38(a) is a block diagram ofthe entire mirror, and FIG. 38(b) is a diagram that cuts the mirror ofFIG. 38(a) in the center of the reflection surface and schematicallyshows the cross section as viewed from the direction of A.

[0332] In FIG. 38, mirror 821 is comprised of multiple mirror elements822, and the reflection surface of each mirror element is movable in thedirection of its normal line. For example, the reflection surface ofmirror element 822 a is flat, and the reflection surface of mirrorelement 822 b is concave, and the reflection surface has moved in thedirection of the normal line.

[0333] The quantity of subduction when it has become concave iscontrolled—that is, the amount of reflection surface movement in thenormal line direction is controlled. For example, it is controlled asillustrated in FIG. 38(b).

[0334] In FIG. 37, the wavelength dispersion compensation device of thisembodiment is equipped with optical circulator 30 as an optical devicethat outputs to a second port (b) light that was inputted to the firstport (a), and outputs to a third port (c) light that was inputted to thesecond port (b).

[0335] Combining/branching device 20 of this embodiment is comprised ofinput slab waveguide 4, input waveguide 3 as an input terminal thatinputs light into this input slab waveguide 4, output slab waveguide 6,and channel waveguide array 5 comprising multiple channel waveguideswith different lengths in which light is inputted from input slabwaveguide 4 and light is outputted to output slab waveguide 6.

[0336] If wavelength division multiplexed light is inputted from the INport (port (a)) of optical circulator 30, the input light generatesangular dispersion with combining/branching device 20 and is branchedinto each wavelength. With an optics system that is comprised ofcylindrical lens 803, lens 804 as an optical device for focusing lightof each wavelength generating this angular dispersion into differentpositions based on the angular dispersion directions, and mirrors 805and 806 as a device for changing light paths, the light is focused onmultiple mirrors 821 corresponding to each wavelength (these lightroutes are called forward paths hereafter).

[0337] The light of each wavelength that is focused at this time has aconstant wavelength spectrum, and if the center wavelength is A, thenlight with wavelength λ−Δλ that is slightly shorter than λ and lightwith wavelength λ+Δλ that is slightly longer than λ also generateangular dispersion with the combining/branching device, and based on itswavelength, this light is focused at different positions than the lightwith wavelength λ.

[0338] Furthermore, the multiple mirror elements 822 are arranged in theline of the direction in which the angular dispersion is generated bythe combining/branching device (the x-axis direction in FIG. 38(b)).Regarding light of each wavelength within the aforementioned wavelengthspectrum, by controlling each mirror element 822 such that the distancesof the optical axis directions of the light are different, it ispossible to control the delay time with each wavelength within thiswavelength spectrum, and functionality as a wavelength dispersioncompensation device is realized.

[0339] Through this embodiment, flattop and low-loss transmissionproperties can be obtained. Moreover, because it is compact and thereare few parts to assemble, it is possible to realize wavelengthdispersion compensation devices as low-loss optical functional deviceswithout troublesome assembly.

[0340] Moreover, in the embodiment of the DGEQ configured using thecombining/branching device of the present invention, it is obvious thatutilization as a wavelength dispersion compensation device is possibleby using the configuration illustrated in FIG. 38 for the mirrorscorresponding to each branched wavelength.

[0341] Furthermore, for the sake of convenience in FIG. 37, the lightpaths of the light of three branched wavelengths are shown and onlythree mirrors 821 corresponding to these are shown, but it is obviousthat the number of branched wavelengths and the number of mirrors 821are not limited to these numbers.

[0342] Embodiment 13

[0343]FIG. 39 is an example embodiment of the optical functional deviceof the present invention as a monitoring device for the light powerlevels of each channel (wavelength) in WDM communications (hereafter,such a device is called an optical power monitor, abbreviated OPM).

[0344] The OPM shown in FIG. 39 is a configuration in which mirror array13 of the DGEQ shown in FIG. 36 is replaced by photoelectric conversionelement array 51 equipped with multiple photoelectric conversionelements 50 as a photoelectric conversion device, and optical circulator30 is removed. Other than these parts, it is identical to theconfiguration shown in FIG. 36.

[0345] In FIG. 39, combining/branching device 20 is comprised of inputslab waveguide 4, input waveguide 3 as an input terminal that inputslight into this input slab waveguide 4, output slab waveguide 6, andchannel waveguide array 5 comprising multiple channel waveguides withdifferent lengths in which light is inputted from input slab waveguide 4and light is outputted to output slab waveguide 6.

[0346] Furthermore, photoelectric conversion elements 50 are arranged asa photoelectric conversion device established in at least one positionin which the light of each wavelength generating angular dispersion withcombining/branching device 20 is nearly focused.

[0347] If wavelength division multiplexed light is inputted from inputwaveguide 3, the input light generates angular dispersion withcombining/branching device 20 and is branched into each wavelength. Withan optical system that is comprised of cylindrical lens 803, lens 804 asan optical device for focusing light of each wavelength generating thisangular dispersion into different positions based on the angulardispersion directions, and mirrors 805 and 806 as a device for changinglight paths, the light is focused on multiple photoelectric conversionelements 50 corresponding to each wavelength. This enables themonitoring of the light power levels of each wavelength, thus fulfillingfunctionality as an OPM.

[0348] As for the photoelectric conversion element array 51 in thisembodiment, the pitch of the optical receiver part is 100 μm and thediameter of the optical receiver part is 50 μm.

[0349] Through this embodiment, flattop and low-loss transmissionproperties can be obtained. Moreover, because it is compact and thereare few parts to assemble, it is possible to realize OPMs as low-lossoptical functional devices without troublesome assembly.

[0350] Furthermore, this can be created using almost all of thecomponents of the DGEQ shown in Embodiment 11 in common.

[0351] Moreover, for the sake of convenience in FIG. 39, the light pathsof light of three branched wavelengths are shown and only threephotoelectric conversion elements 50 corresponding to these are shown,but it is obvious that the number of branched wavelengths and the numberof photoelectric conversion elements 50 are not limited to thesenumbers.

[0352] Embodiment 14

[0353]FIG. 40 is an embodiment of the optical functional device of thepresent invention as a wavelength selective switch in a WDMcommunications system.

[0354] In FIG. 40, the wavelength selective switch of this embodiment isequipped with optical circulators 30 and 31 as an optical device thatoutput to a second port (b) light that was inputted to the first port(a), and outputs to a third port (c) light that was inputted to thesecond port (b), and these optical circulators 30 and 31 are connectedto the input terminals of combining/branching devices 20 and 21,respectively.

[0355] Furthermore, combining/branching devices 20 and 21 of thisembodiment are comprised of input slab waveguide 4, input waveguide 3 asan input terminal that inputs light into this input slab waveguide 4,output slab waveguide 6, and channel waveguide array 5 comprisingmultiple channel waveguides with different lengths in which light isinputted from input slab waveguide 4 and light is outputted to outputslab waveguide 6.

[0356] In FIG. 40, if wavelength division multiplexed light is sent tothe IN port of optical circulator 30, it is guided to input waveguide 3of the first combining/branching device 20. The light freely propagatesthrough input slab waveguide 4, reaches channel waveguide array 5, andoptically couples, so the power of the input light is distributed to allof the channel waveguides that constitute channel waveguide array 5.

[0357] The light within each channel waveguide that constitutes channelwaveguide array 5 causes phase shifts corresponding to its wavelengthand it is outputted from the output terminal, and exits as parallellight in an angular dispersion direction based on each wavelength.

[0358] Light that is branched into each wavelength by channel waveguidearray 5 in this way is led to cylindrical lens 803, and becomes parallellight with respect to the vertical direction.

[0359] This is the same for the case in which wavelength divisionmultiplexed light is sent to the ADD port of optical circulator 31.

[0360] Moreover, lenses 804 are respectively established as a device forfocusing (a) light of each wavelength that generates angular dispersionwith the first combining/branching device 20 and (b) light of the samewavelength that generates angular dispersion with the secondcombining/branching device 21 into different positions based on theangular dispersion directions.

[0361] Furthermore, these lenses 804 and mirrors 805 and 807 arearranged such that (a) the position in which light of a frequencygenerating angular dispersion with the first combining/branching device20 is focused and (b) the position in which the light of the samefrequency generating angular dispersion with the secondcombining/branching device 21 is focused are in agreement.

[0362] Moreover, mirror array 13 comprising multiple mirrors 801 isarranged as a light reflection device that is established in at leastone position in which light of each frequency generating this angulardispersion is nearly focused, and light of each frequency branched bythe first combining/branching device is fed into this array.

[0363] Mirrors 801 corresponding to each branched wavelength arearranged on mirror array 13. The angle of each mirror is adjusted asnecessary, and light from the first combining/branching device 20 iseither returned to the first combining/branching device 20 or it isreflected to the second combining/branching device 21.

[0364] In other words, regarding light with a wavelength in whichswitching is not performed from among wavelength division multiplexedlight sent to the first combining/branching device 20, the reflectionangle of the mirror in the position corresponding to that wavelength isadjusted such that the light from the first combining/branching device20 returns to the first combining/branching device 20.

[0365] On the other hand, regarding light with a wavelength in whichswitching is performed, the reflection angle of the mirror in theposition corresponding to that wavelength is adjusted such that thelight from the first combining/branching device 20 is led to the secondcombining/branching device 21. At this time, light with the samewavelength from the second combining/branching device 21 is reflectedwith this mirror and led to the first combining/branching device 20.

[0366] In this way, the function of a wavelength selective switch, whichis an optical functional device that can (a) drop light of prescribedwavelength from among wavelength division multiplexed light that enteredthe IN port of optical circulator 30 and lead it to the DROP port ofoptical circulator 31, and (b) add light with the same wavelength as thedropped wavelength from among wavelength division multiplexed light thatentered the ADD port of optical circulator 31 and output it from the OUTport of optical circulator 30 as wavelength division multiplexed light,is fulfilled.

[0367] In this way, through this embodiment, flattop and low-losstransmission properties can be obtained. Moreover, because it is compactand there are few parts to assemble, it is possible to realizewavelength selective switches as low-loss optical functional deviceswithout troublesome assembly.

[0368] Furthermore, because it is possible to use a configurationresembling those of Embodiments 10˜13 for an optical system comprised ofcombining/branching devices, cylindrical lens 803, lenses 804, andmirrors 805 and 807, there is no need to separately develop this partfor a wavelength selective switch, and there is also the effect ofreducing costs due to mass production of common parts.

[0369] For example, the wavelength selective switch shown in thisembodiment is configured such that the DGEQ shown in FIG. 36 isaxisymmetrically arranged and array 13 of mirrors 801 and mirror 806 areshared.

[0370] Moreover, for the sake of convenience in FIG. 40, the light pathsof light of three branched wavelengths are shown and only three mirrors801 corresponding to these are shown, but it is obvious that the numberof branched wavelengths and the number of mirrors 801 are not limited tothese numbers.

[0371] Embodiment 15

[0372]FIG. 41 is an embodiment of the optical functional device of thepresent invention as an OPM in a WDM communications system, and itfulfills the same function as the OPM shown in FIG. 39.

[0373] The difference between the configuration of FIG. 41 and theconfiguration of FIG. 39 is that a portion of the functionality of thecomponents of the free-space optical system in FIG. 39 is realizedinside of output slab waveguide 6.

[0374] In FIG. 41, slab waveguide interior end faces 603 and 604, inwhich the lines drawn by the edges when the end faces inside the slabwaveguide are projected against the primary plane of slab substrate 100are straight lines, are formed such that they are approximatelyperpendicular to the primary plane of slab substrate 100, such that thelight that freely propagates within the core pattern of output slabwaveguide 6 is reflected in a direction that is parallel to the primaryplane of slab substrate 100, thus fulfilling the function of mirror 805in FIG. 39.

[0375] Here, “the line drawn by the edge when the end face inside theslab waveguide is projected against the primary plane of the slabsubstrate” refers to, “the line drawn by the slab waveguide interior endface (for example, 603) when viewed from directly above slab substrate100.”

[0376] Slab waveguide interior end face 605, in which the line drawn bythe edge when projected against the primary plane of the slab substrateis a curve, is established inside output slab waveguide 6. It is thereflection surface that focuses light of each wavelength generatingangular dispersion with combining/branching device 20 into differentpositions based on the angular dispersion directions, and it thusfulfills the function of lens 804 in FIG. 39.

[0377] Moreover, as stated previously, output slab waveguide 6 enclosesa core having a relatively high index of refraction with a clad having arelatively low index of refraction, so light is trapped within the core.This shows that the functionality of cylindrical lens 803 of FIG. 39 isalso realized in the configuration of FIG. 41.

[0378] Furthermore, by configuring slab waveguide interior end face 605such that the line drawn by the edge when projected against the primaryplane of the slab substrate is a parabola, it is possible to realizefunctionality that concentrates parallel light beams onto a single pointwithout aberration, and transforms light beams emitted from a lightsource that can be considered a point source into parallel light with noaberration.

[0379] In other words, as shown in FIG. 13, light outputted from channelwaveguide array 5 propagates through the inside of output slab waveguide6 as parallel light facing a different direction based on eachwavelength. By reflecting with end face 605, in which the line drawn bythe edge when this parallel light is projected against the primary planeof the slab substrate is a parabola, it is possible to cause the lightto converge.

[0380] Furthermore, by arranging photoelectric conversion element array51 such that photoelectric conversion elements 50 are arranged as aphotoelectric conversion device corresponding to positions in which ofthis light of each wavelength is nearly focused, it functions as an OPMthat monitors the light power level of each channel (wavelength).

[0381] Moreover, by changing light paths by 90 degrees with mirror 806,this embodiment enables the mounting of slab substrate 100 andphotoelectric element array 51 on the same plane.

[0382] In this way, in this embodiment as well, as with Embodiment 14described previously, flattop and low-loss transmission properties canbe obtained. Moreover, because it is compact and there are few parts toassemble, it is possible to realize OPMs as low-loss optical functionaldevices without troublesome assembly.

[0383] Moreover, optical systems having slab interior waveguide endfaces on output slab waveguide 6 in this way are called slab opticalsystems hereafter, and slab optical systems having slab interiorwaveguide end faces resulting from curved surfaces such as thatillustrated by slab interior waveguide end face 605 in FIG. 41 arecalled focusing type slab optical systems.

[0384] Here, (a) the core that constitutes input waveguide 3, input slabwaveguide 4, and channel waveguide array 5, and (b) the core thatconstitutes output slab waveguide 6 as a focusing type slab opticalsystem can be formed simultaneously with the same materials in thethickness direction, so it has the effect in which they areautomatically aligned.

[0385] Furthermore, slab interior waveguide end faces 603, 604, and 605can be formed by printing images of patterns formed on photomasks in thesame manner as in semiconductor manufacturing processes.

[0386] For example, for the realization of free-space optical systemsconfigured with the cylindrical lens 803, lens 804, and mirror 805 ofFIG. 39, because it is required that these parts are precisely alignedand fixated, assembly and adjustment require labor and time.

[0387] In contrast to this, by using a slab optical system, an opticalsystem having the same functionality can be realized by simply designingmask patterns, and this generates the effect that manufacturing becomeseasy.

[0388]FIG. 42 is a diagram that shows an example of a slab opticalsystem, and it has the same configuration as the part of output slabwaveguide 6 of FIG. 41.

[0389] As shown in FIG. 42, in the method that separately manufacturesthe output slab waveguide only and joins and optically couples thecombining/branching device parts illustrated in FIG. 39, for example,the effect is generated that manufacturing becomes easier than when anoptical system is configured by separately using cylindrical lens 803,lens 804, and mirror 805.

[0390] Furthermore, the number, shape, and arrangement of the reflectionsurfaces comprised of slab waveguide end faces can, of course, bechanged as necessary.

[0391]FIG. 43 is an example of another configuration of a slab opticalsystem. It is a configuration in which the reflection surface thatconstitutes the slab waveguide end face is broken into two slabwaveguide end faces, 603 and 605, and this reflection surface isarranged on the end face or in the vicinity of the end face of the slabsubstrate. This configuration generates the effect that the formation ofhigh-reflectivity films and low-reflectivity films on the reflectionsurface becomes easy.

[0392] Next, the concrete structure of the OPM shown in FIG. 41 will beexplained.

[0393] The core that constitutes output slab waveguide 6 in FIG. 41 canbe manufactured simultaneously and with the same materials as the corethat constitutes a wavelength combining/branching filter, so its indexof refraction and thickness are the same as the core that constitutes awavelength combining/branching filter, and it is formed consecutivelywith the core pattern for the channel waveguide array.

[0394] Slab waveguide interior end faces 603, 604, and 605 are formedthrough reactive ion etching after the core is embedded by clads. Aphotolithography process is used for this manufacturing process, so theshapes and relative positions of slab waveguide interior end faces 603,604, and 605 are determined by patterns formed on glass masks.

[0395] The thickness, width, and length of waveguides and the core/cladindex of refraction difference are the same as in Embodiment 1.

[0396] The dimensions of the slab optical system are as follows. Thedistance from the output apertures of the core pattern for the channelwaveguide array to slab waveguide interior end face 603 is approximately45 mm, the distance along the light path from the output apertures ofthe core pattern for the channel waveguide array to slab waveguideinterior end face 605 is 85 mm, and the curvature radius of slabwaveguide interior end face 605 is 200 mm.

[0397] The distance along the light path from slab waveguide interiorend face 605 to focus position 701 is approximately 100 mm. The pitchbetween the optical receiver parts of each photoelectric conversionelement 50 of photoelectric conversion element array 51 is 100 μm, andthe diameter of optical receiver parts is 50 μm.

[0398] Moreover, a cylindrical lens for the purpose of focusing on focusposition 701 light that radiates in directions perpendicular to theprimary plane of the slab substrate may be arranged on the part in whichthe light propagates through the slab optical system.

[0399] Moreover, for the sake of convenience in FIG. 41, the light pathsof light of three branched wavelengths are shown and only threephotoelectric conversion elements 50 corresponding to these are shown,but it is obvious that the number of branched wavelengths and the numberof photoelectric conversion elements 50 are not limited to thesenumbers.

[0400] Embodiment 16

[0401]FIG. 44 is an embodiment of the optical functional device of thepresent invention as an OPM in a WDM communications system, and itfulfills the same function as the OPM shown in FIG. 41.

[0402] The difference between the configuration of FIG. 44 and theconfiguration of FIG. 41 is that FIG. 44 of this embodiment is aconfiguration in which (a) mirror 806, which is a component of thefree-space optical system in FIG. 41, is not established, (b) position701 in which light that generates angular dispersion is focused isbrought together with the last end face 606 of the focusing type slaboptical system, and (c) photoelectric conversion element array 51 isattached to this end face.

[0403] In this embodiment as well, as with Embodiment 15 describedpreviously, flattop and low-loss transmission properties can beobtained. Moreover, because it is compact and there are few parts toassemble, it is possible to realize OPMs as low-loss optical functionaldevices without troublesome assembly.

[0404] Furthermore, through this embodiment, effects are generated inwhich, in comparison to Embodiment 15, the number of parts is furtherreduced and the cost decreases, the number of necessary points for partalignment decreases and the configuration of the optical system becomeseasy, the stability of the optical system improves due to the fact thatposition misalignment of parts is less likely to occur, and it becomescompact.

[0405] Moreover, in FIG. 44, the curvature radius of slab waveguideinterior end face 605 is approximately 180 mm.

[0406] Moreover, for the sake of convenience in FIG. 44, the light pathsof light of three branched wavelengths are shown and only threephotoelectric conversion elements 50 corresponding to these are shown,but it is obvious that the number of branched wavelengths and the numberof photoelectric conversion elements 50 are not limited to thesenumbers.

[0407] Embodiment 17

[0408]FIG. 45 is an embodiment of the optical functional device of thepresent invention, a DGEQ in a WDM communications system, and itfulfills the same function as the DGEQ shown in FIG. 36.

[0409] The relationship between this embodiment and Embodiment 11 is thesame as the relationship between Embodiment 15 and Embodiment 13.

[0410] In other words, the difference between the configuration of thisembodiment shown in FIG. 45 and the configuration shown in FIG. 36 isthat a portion of the functionality of the components of the free-spaceoptical system in FIG. 36 is realized inside of output slab waveguide 6.

[0411] In FIG. 45, slab waveguide interior end faces 603 and 604 areformed such that they are approximately perpendicular to the primaryplane of slab substrate 100, such that the light that freely propagateswithin the core pattern of output slab waveguide 6 is reflected in adirection that is parallel to the primary plane of slab substrate 100,thus fulfilling the function of mirror 805 in FIG. 36.

[0412] Slab waveguide interior end face 605, in which the line drawn bythe edge when projected against the primary plane of slab substrate 100is a curve, is established inside output slab waveguide 6. It is thereflection surface that focuses light of each wavelength generatingangular dispersion with combining/branching device 20 into differentpositions based on the angular dispersion directions, and it thusfulfills the function of lens 804 in FIG. 36.

[0413] Furthermore, it operates in the same manner as Embodiment 11, andfulfills the function as a DGEQ.

[0414] In this embodiment as well, as with Embodiment 14 describedpreviously, flattop and low-loss transmission properties can beobtained. Moreover, because it is compact and there are few parts toassemble, it is possible to realize DGEQs as low-loss optical functionaldevices without troublesome assembly.

[0415] Furthermore, through this embodiment, due to the fact that thecombining/branching device and the focusing type slab optical system areformed as a unit, effects are generated in which the number of parts isreduced and the cost decreases, the number of necessary points for partalignment decreases and the configuration of the optical system becomeseasy, the stability of the optical system improves due to the fact thatposition misalignment of parts is less likely to occur, and it becomescompact.

[0416] Moreover, for the sake of convenience in FIG. 45, the light pathsof light of three branched wavelengths are shown and only three mirrors801 corresponding to these are shown, but it is obvious that the numberof branched wavelengths and the number of mirrors 801 are not limited tothese numbers.

[0417] Embodiment 18

[0418]FIG. 46 is an embodiment of the optical functional device of thepresent invention as a DGEQ in a WDM communications system, and itfulfills the same function as the DGEQ shown in FIG. 45.

[0419] The difference between the configuration of this embodiment shownin FIG. 46 and the configuration shown in FIG. 45 is that the functionof mirrors 805 that constitute the free-space optical system in FIG. 45is realized inside of output slab waveguide 6, and other components areidentical to FIG. 45.

[0420] In other words, mirror 806, which was necessary in FIG. 45, ismade unnecessary by establishing slab waveguide interior end face 607,which is inclined with respect to the primary plane of slab substrate100, inside output slab waveguide 6 in FIG. 46, and guiding light thatpropagates through the output slab waveguide with this inclined plane ina direction perpendicular to slab substrate 100. As with theconfiguration shown in FIG. 45, it is possible to simplify mounting bymaking parallel the primary plane of mirror array 13 and the primaryplane of slab substrate 100.

[0421] Furthermore, in this embodiment as well, it operates in the samemanner as Embodiment 11, and is obvious that it fulfills the function asa DGEQ.

[0422] Moreover, in this embodiment as well, flattop and low-losstransmission properties can be obtained. Moreover, because it is compactand there are few parts to assemble, it is possible to realize DGEQs aslow-loss optical functional devices without troublesome assembly.

[0423] Furthermore, through this embodiment, due to the fact that thecombining/branching device and the focusing type slab optical system areformed as a unit, effects are generated in which the number of parts isreduced and the cost decreases, the number of necessary points for partalignment decreases and the configuration of the optical system becomeseasy, the stability of the optical system improves due to the fact thatposition misalignment of parts is less likely to occur, and it becomescompact.

[0424] Moreover, for the sake of convenience in FIG. 46, the light pathsof light of three branched wavelengths are shown and only three mirrors801 corresponding to these are shown, but it is obvious that the numberof branched wavelengths and the number of mirrors 801 are not limited tothese numbers.

[0425] Embodiment 19

[0426]FIG. 47 is an embodiment of the optical functional device of thepresent invention as a wavelength selective switch in a WDMcommunications system, and it fulfills the same function as thewavelength selective switch shown in FIG. 40.

[0427] The relationship between this embodiment and Embodiment 14 is thesame as the relationship between Embodiment 15 and Embodiment 13.

[0428] In other words, the difference between the configuration of thisembodiment shown in FIG. 47 and the configuration shown in FIG. 40 isthat a portion of the functionality of the components of the free-spaceoptical system in FIG. 40 is realized inside of output slab waveguide 6.

[0429] In FIG. 47, slab waveguide interior end faces 603 and 604 areformed such that they are approximately perpendicular to the primaryplane of slab substrate 100, such that the light that freely propagateswithin the core pattern of output slab waveguide 6 is reflected in adirection that is parallel to the primary plane of slab substrate 100,thus fulfilling the function of mirror 805 in FIG. 40.

[0430] Slab waveguide interior end face 605, in which the line drawn bythe edge when projected against the primary plane of slab substrate 100is a curve, is established inside output slab waveguide 6. It is thereflection surface that focuses light of each wavelength generatingangular dispersion with combining/branching device 20 into differentpositions based on the angular dispersion directions, and it thusfulfills the function of lens 804 in FIG. 40. This is the same withrespect to the output slab waveguide of combining/branching device 21.

[0431] Moreover, it operates in the same manner as Embodiment 15, andfulfills the function as a wavelength selective switch.

[0432] In this embodiment as well, flattop and low-loss transmissionproperties can be obtained. Moreover, because it is compact and thereare few parts to assemble, it is possible to realize wavelengthselective switches as low-loss optical functional devices withouttroublesome assembly.

[0433] Furthermore, through this embodiment, the combining/branchingdevice and the focusing type slab optical system are formed as a unit,so effects are generated in which the configuration of the opticalsystem becomes easy, the stability of the optical system improves due tothe fact that position misalignment of parts is less likely to occur,and it becomes compact.

[0434] Moreover, a portion or all of the waveguides that constitute thisembodiment may be simultaneously created on the same slab substrate.

[0435] Moreover, for the sake of convenience in FIG. 47, the light pathsof light of three branched wavelengths are shown and only three mirrors801 corresponding to these are shown, but it is obvious that the numberof branched wavelengths and the number of mirrors 801 are not limited tothese numbers.

[0436] Embodiment 20

[0437]FIG. 48 is an embodiment of the optical functional device of thepresent invention as a wavelength selective switch in a WDMcommunication system, DGEQ, and OPM composite device. Fulfilling eachfunction, it is a configuration in which the combining/branching deviceand the slab optical system of the present invention are formed as aunit.

[0438] In FIG. 48, combining/branching device 20, combining/branchingdevice 21, the slab optical systems of these, mirror array 13, andauxiliary circuit 401 that controls the mirrors form a wavelengthselective switch that is approximately the same as the configurationshown in FIG. 47.

[0439] Here, slab waveguide interior end face 607 of the output terminalof the slab optical system is inclined with respect to the primary planeof slab substrate 100, and it is arranged such that light of eachwavelength branched by combining/branching device 20 and light of eachwavelength branched by combining/branching device 21 are respectivelyguided to the corresponding mirrors of mirror array 13 that is mountedon substrate 400, which is roughly parallel to the primary plane of slabsubstrate 100, and light of the same wavelength is focused on the samemirror, thus fulfilling the function of mirror 807 in FIG. 47.

[0440] Light of a prescribed wavelength from among wavelength divisionmultiplexed light that is inputted to the IN1 port of optical circulator34 is outputted from the DROP port of optical circulator 35. Light ofother wavelengths is combined with light having the same wavelength asthis prescribed wavelength that is inputted from the ADD port of opticalcirculator 35, and it is outputted from the OUT1 port of opticalcirculator 34, thus fulfilling the function of a wavelength selectiveswitch.

[0441] Wavelength division multiplexed light that is outputted from theOUT1 port of optical circulator 35 is inputted to the IN2 port ofoptical circulator 36.

[0442] Combining/branching device 23, the slab optical system ofcombining/branching device 23, photoelectric conversion element array51, and auxiliary circuit 402, which processes electrical signals fromeach photoelectric conversion element and controls the photoelectricconversion elements, form an OPM that is approximately the same as theconfiguration shown in FIG. 41.

[0443] A portion of wavelength division multiplexed light that isinputted to the IN2 port of optical circulator 36 is guided tocombining/branching device 23 for monitoring, where it generates angulardispersion and is branched. It is focused on the photoelectricconversion element corresponding to each wavelength of photoelectricconversion element array 51 and its intensity is monitored, thusrealizing the function of an OPM.

[0444] Combining/branching device 24, the slab optical system ofcombining/branching device 24, mirror array 14, and auxiliary circuit403, which controls mirror array 14, form a DGEQ that is approximatelythe same as the configuration shown in FIG. 41.

[0445] Here, slab waveguide interior end face 608 of the output terminalof the slab optical system of combining/branching device 24 is inclinedwith respect to the primary plane of slab substrate 100, and it isarranged such that light of each wavelength branched bycombining/branching device 24 is respectively guided to thecorresponding mirrors of mirror array 14 that is mounted on substrate300, which is roughly parallel to the primary plane of slab substrate100, thus fulfilling the function of mirror 806 in FIG. 41.

[0446] Light other than the aforementioned light that is branched formonitoring from among wavelength division multiplexed light that isinputted to the IN2 port of the aforementioned optical circulator 36 isguided to combining/branching device 24, where it generates angulardispersion and is branched into each wavelength.

[0447] It is focused on the corresponding mirrors of mirror array 14,causing prescribed attenuation, and it is outputted as wavelengthdivision multiplexed light from the OUT2 port of optical circulator 36.The function of a DGEQ can thus be realized.

[0448] As described above, by using the optical functional device ofthis embodiment, it is possible to (a) add and drop prescribedwavelengths with respect to wavelength division multiplexed lighttransmitted from a terminal, for example, (b) monitor the resultingwavelength division multiplexed light for each wavelength, and (c)regulate each wavelength to prescribed light levels.

[0449] In this embodiment as well, flattop and low-loss transmissionproperties can be obtained. Moreover, because it is compact and thereare few parts to assemble, it is possible to realize low-loss opticalfunctional devices without troublesome assembly.

[0450] Furthermore, through this embodiment, the alignment of partsconfigured with light guides and mirrors and photoelectric conversionelements can be performed together at once, which results in the effectthat the labor of alignment is reduced. Additionally, it is alsopossible to perform optical fiber connections together at once, whichresult in the effect that the labor of fiber connection is reduced.

[0451] Moreover, for the sake of convenience in FIG. 48, the light pathsof light of three branched wavelengths are shown and only three mirrorsthat constitute mirror array 13, 3 photoelectric conversion elementsthat constitute photoelectric conversion element array 51, and 3 mirrorsthat constitute mirror array 14 are shown, but it is obvious that thenumber of branched wavelengths and the numbers of mirrors andphotoelectric conversion elements are not limited to these numbers.

[0452] Moreover, this embodiment is configured such that the functionsof the wavelength selective switch, the OPM, and the DGEQ are realizedone by one in this order, but the combination of these functions, thenumber realized, and their order can be selected as necessary.

[0453] Embodiment 21

[0454]FIG. 49 is an embodiment applied to a WDM transmission systemusing the optical functional device of the present invention, and itshows the configuration of point B having the function of dividing eachchannel (wavelength) of wavelength division multiplexed light from pointA into the directions of point C and point D.

[0455] Moreover, this configuration of point B has (a) the function ofadding and dropping specific channels to and from wavelength divisionmultiplexed light heading towards points C and D, (b) the function of anOPM that monitors the light intensity of each channel that constitutesthe wavelength division multiplexed light, and (c) the function of aDGEQ that adjusts the attenuation of light of each channel.

[0456] In FIG. 49, wavelength division multiplexed light from point A isinputted to the IN1 port of wavelength selective switch 61. Light fromspecific channels is outputted from the OUT1 port and divided into thedirection of point C, while light from the other channels is outputtedfrom the DROP1 port and divided into the direction of point D.

[0457] At this time, it is possible to input wavelength divisionmultiplexed light to the ADD1 port, add light of the same channels(wavelength) as the channels that were divided into the direction ofpoint D to wavelength division multiplexed light that is outputted fromthe OUT1 port, and transmit it towards point C.

[0458] This wavelength division multiplexed light heading towards pointC approaches point C by way of DGEQ 63, and a portion of this isinputted to OPM 65. The intensity of light of each channel thatconstitutes the wavelength division multiplexed light can be measuredwith OPM 65, and the intensity of light of specific channels can beadjusted as necessary with DGEQ 63.

[0459] For example, each channel of wavelength division multiplexedlight heading towards point C is comprised of a channel that uses pointA as a transmission source and an additional channel that uses point Bas a transmission source, and cases in which the intensities of lightsignificantly differ due to this difference in transmission sources anddifferences in transmission routes, for example, can be considered.However, through this embodiment, it is possible to monitor and regulatethe intensities of light of each channel, and it is possible to transmitlight in the direction of point C after making the intensities of lightof each channel roughly equivalent.

[0460] Moreover, wavelength division multiplexed light heading towardspoint D that is outputted from the DROP1 port of wavelength selectiveswitch 61 is inputted to the IN2 port of wavelength selective switch 62.It is possible to output light of specific channels from the DROP2 port,and utilization at point B—for example, converting it into electricalsignals, or transferring it to other points—is possible.

[0461] Furthermore, light of channels other than the channels outputtedfrom this DROP2 port is outputted from the OUT2 port towards point D,but at this time it is possible to input wavelength division multiplexedlight to the ADD2 port, add light of the same channels as the channelsthat were outputted from the DROP2 port to wavelength divisionmultiplexed light that is outputted from the OUT2 port, and transmit ittowards point D.

[0462] Moreover, DGEQ 64 and OPM 66 are able to provide to wavelengthdivision multiplexed light heading towards point D the same operationsand effects as the aforementioned DGEQ 63 and OPM 65.

[0463] The optical functional devices shown in all of the aforementionedembodiments are applicable to the wavelength selective switch, DGEQ, andOPM of this embodiment. For example, they may assume the configurationsshown in FIG. 40, FIG. 36, and FIG. 39, respectively, or they may assumethe configuration shown in FIG. 48.

[0464] By using this embodiment, it becomes possible to directlydistribute light arbitrary channels (wavelengths) to multiple routes,and it generates the effect in which the cost of the system reduces incomparison to the case in which the light is first converted intoelectrical signals.

[0465] According to above embodiments of the present invention, anoptical functional device comprises a first light combining/branchingdevice and a second combining/branching device including an inputwaveguide, a slab waveguide, and a channel waveguide array comprisingmultiple channel waveguides with differing lengths. An optical devicefocuses light that is branched by the first and second lightcombining/branching devices. A light reflector is arranged in theposition of convergence of the branched light, having a variablereflection angle. Based on the reflection angle of the light reflector,the light path in which light of at least one wavelength radiated fromthe first light combining/branching device enters the second lightcombining/branching device and the light path in which this lightreturns to the first light combining/branching device can be selected.

[0466] According to embodiments of the present invention, an opticalfunctional device comprises a light combining/branching devicecontaining an input waveguide, a slab waveguide, and a channel waveguidearray comprising multiple channel waveguides with differing lengths. Anoptical device focuses light that is branched by the lightcombining/branching device. A light reflector is arranged in theposition of convergence of the branched light, and has a variablereflection angle.

[0467] According to embodiments of the present invention, an opticalfunctional device comprises a light combining/branching devicecontaining an input waveguide, a slab waveguide, and a channel waveguidearray comprising multiple channel waveguides with differing lengths. Anoptical device focuses light that is branched by the lightcombining/branching device. A light reflector is arranged in theposition of convergence of the branched light, and is able to move thereflection position in the traveling direction of the incident light. Itis possible to regulate the light path length of light that returns tothe light combining/branching device within the wavelength spectrum ofincident light by changing the reflection position of the lightreflector within the wavelength spectrum of the incident light.

[0468] According to embodiments of the present invention, an opticalaxis conversion device transforms the light path by 90 degrees betweenthe light combining/branching device and the light reflector, where theprimary surfaces of the substrates on which the lightcombining/branching device and the light reflector are mounted areparallel.

[0469] According to embodiments of the present invention, an opticalfunctional device comprises a light combining/branching device thatdivides light of each wavelength that constitutes wavelength divisionmultiplexed light into two or more wavelength groups, and multiplexesthe wavelength division multiplexed light of each of the wavelengthgroups.

[0470] According to embodiments of the present invention, opticalfunctional devices are connected to each of the branching side ports ofa light combining/branching device.

[0471] According to embodiments of the present invention, an opticalfunctional device includes a planar light guide comprising a slabsubstrate having a primary plane, a clad formed on the primary plane ofthe slab substrate, a core that has a higher index of refraction thanthe clad and is enclosed by the clad, and a waveguide end face in whichthe cross sections of the clad and the core are exposed by a surfacethat is perpendicular to the slab substrate. Core patterns for a channelwaveguide array in which (A) the light guide is comprised of (a) a corepattern for input waveguides in which one end of the core reaches thewaveguide end face, and (b) multiple independent core patterns in whichone side is used as input apertures and the other side is used as outputapertures, and (B) the core patterns are configured such that the lightpath differences between the input apertures and the output apertures ofadjacent core patterns are constant. Core patterns for the input slabare connected to the input waveguide core pattern and the inputapertures of the channel waveguide array core patterns. The inputapertures of the channel waveguide array core patterns are arranged onthe arc of a first circle having radius R, the input waveguide corepattern is formed on a Rowland circle of the first circle, and theoutput apertures of the channel waveguide array core patterns arearranged in a straight line at constant intervals. Light that enters theinput waveguide core pattern of the light guide end face passes throughthe input waveguide core pattern and reaches an input slab core pattern,after which the light freely propagates within the input slab corepattern in the direction of the primary plane of the slab substrate, andoptically couples with the plurality of the channel waveguide array corepatterns. The input waveguide core pattern, the input slab core pattern,and the channel waveguide array core patterns are arranged such that,after light passes through the channel waveguide array core patterns, itbecomes approximately parallel light and is diffracted from the outputapertures of the channel waveguide array core patterns in the directionof the primary plane of the slab substrate and in directionscorresponding to the wavelengths.

[0472] According to various embodiments of the present invention, anoutput slab core pattern formed connected to the output apertures of thechannel waveguide array core patterns is established. According tovarious embodiments of the present invention, a slab interior waveguideend face, which is a waveguide end face for the purpose of reflectinglight that is transmitted in the direction of the primary plane of theslab substrate, is on the inside of the output slab core pattern.Further, according to various embodiments of the present invention, theslab interior waveguide end face focuses almost all light, whichgenerates angular dispersion and is outputted as parallel light from theoutput apertures of the channel waveguide array core patterns, in adirection that is parallel to the primary plane of the slab substrate.

[0473] According to additional embodiments of the present invention, aslab interior waveguide end face in which the line drawn by the edgewhen the slab interior waveguide end face is projected against theprimary plane of the slab substrate is a curved line.

[0474] According to various embodiments of the present invention, theline drawn by the edge when the slab interior waveguide end face isprojected against the primary plane of the slab substrate is an arc.

[0475] Further, according to embodiments of the present invention, theline drawn by the edge when the slab interior waveguide end face isprojected against the primary plane of the slab substrate is a parabola.

[0476] According to embodiments of the present invention, a slabinterior waveguide end face in which the line drawn by the edge when theslab interior waveguide end face is projected against the primary planeof the slab substrate is a straight line. A slab interior waveguide endface in which the line drawn by the edge when the slab interiorwaveguide end face is projected against the primary plane of the slabsubstrate is a curved line. The end faces are arranged such that theyfocus almost all light, which generates angular dispersion and isoutputted as parallel light from output apertures of the channelwaveguide array core patterns, in a direction that is parallel to theprimary plane of the slab substrate.

[0477] According to embodiments of the present invention, an opticalfunctional device has, on the inside of the output slab core pattern, aninclined waveguide end face that is inclined with respect to the primaryplane of the slab substrate. Light is reflected with the inclinedwaveguide end face and light is emitted to the outside of the waveguide.

[0478] According to embodiments of the present invention, a lightreflector is able to change the relative angles of the incident lightand the reflection surface is established in a position in which of thelight is nearly focused.

[0479] According to embodiments of the present invention, a lightreflector is able to change the position of the reflection surface,which is perpendicular to the incident light, to the traveling directionof the incident light. The light reflector is established correspondingto each wavelength in a position in which the light is nearly focused.

[0480] According to embodiments of the present invention, aphotoelectric converter is established corresponding to each wavelengthin a position in which the light is nearly focused such that itoptically couples with incident light.

[0481] According to embodiments of the present invention, a planar lightguide includes a slab substrate having a primary plane, a clad formed onthe primary plane of the slab substrate, a core that has a higher indexof refraction than the clad and is enclosed by the clad, and a waveguideend face in which the cross sections of the clad and the core areexposed by a surface that is perpendicular to the slab substrate. Corepatterns for a channel waveguide array in which (A) the light guide iscomprised of (a) a core pattern for input waveguides in which one end ofthe core reaches the waveguide end face, and (b) multiple independentcore patterns in which one side is used as input apertures and the otherside is used as output apertures, and (B) the core patterns areconfigured such that the light path differences between the inputapertures and the output apertures of adjacent core patterns areconstant. Core patterns for the input slab are formed connected to theinput waveguide core pattern and the input apertures of the channelwaveguide array core patterns. The input apertures of the channelwaveguide array core patterns are arranged on the arc of a first circlehaving radius R, the input waveguide core pattern is formed on a Rowlandcircle of the first circle, and the output apertures of the channelwaveguide array core patterns are arranged in a straight line atconstant intervals. An output slab core pattern is formed connected tothe output apertures of the channel waveguide array core pattern. On theinside of the output slab core pattern, a first optical functionaldevice and a second optical functional device have a slab interiorwaveguide end face, which is a waveguide end face for the purpose of (a)reflecting light that is transmitted in the direction of the primaryplane of the slab substrate and (b) focusing almost all light, whichgenerates angular dispersion and is outputted as parallel light from theoutput apertures of the channel waveguide array core patterns, in adirection that is parallel to the primary plane of the slab substrate.Each of the optical functional devices are arranged such that thepositions in which the light is nearly focused are common, and a lightreflector that is able to change the relative angles of the incidentlight and the reflection surface is established in this position inwhich the light is nearly focused.

[0482] According to embodiments of the present invention, multipleoptical functional devices are formed on the same slab substrate as aunit.

[0483] Moreover, according to embodiments of the present invention, aconvex lens is established on the transmission route of light that isoutputted to the exterior of a planar light guide such that its focalpoint is positioned on the output apertures of the channel waveguidearray core patterns. A light reflector is established at the focal pointposition of the convex lens on the opposite side as the planar lightguide.

[0484] According to embodiments of the present invention, a convex lensis established on the transmission route of light that is outputted tothe exterior of the planar light guide such that its focal point ispositioned on the output apertures of the channel waveguide array corepatterns. A light reflector is able to change the position of thereflection surface, which is perpendicular to the incident light, to thetraveling direction of the incident light. The light reflector isestablished at the focal point position of the convex lens on theopposite side as the planar light guide.

[0485] According to embodiments of the present invention, a convex lensis established on the transmission route of light that is outputted tothe exterior of the planar waveguide such that its focal point ispositioned on the output apertures of the channel waveguide array corepatterns. A photoelectric converter is established at the focal pointposition of the convex lens on the opposite side as the planar lightguide such that it optically couples with incident light.

[0486] According to embodiments of the present invention, multipleoptical functional devices are established. A convex lens is establishedon the transmission route of light that is outputted to the exterior ofa planar light guide of each optical functional device such that itsfocal point is positioned on the output apertures of channel waveguidearray core patterns. Each of the optical functional devices and theconvex lenses are arranged such that the focal point position of theconvex lens on the opposite side as the planar light guide becomes thesame focal point position for light of the same wavelength that isoutputted to the exterior of each the optical functional devices. Alight reflector is able to change the relative angles of the incidentlight, and the reflection surface is established at the focal pointposition of the convex lens on the opposite side as the planar lightguide.

[0487] According to embodiments of the present invention, it is possibleto realize optical functional devices that have flattop transmissionproperties, have small loss, and are compact.

[0488] Various example dimensions and measurements are described herein.However, the present invention is not limited to any specific dimensionsand/or measurements. For example, the present invention is not limitedto the numbers of channels, spacing of layers/devices, and devicemeasurements described herein.

[0489] Although a few preferred embodiments of the present inventionhave been shown and described, it would be appreciated by those skilledin the art that changes may be made in these embodiments withoutdeparting from the principles and spirit of the invention, the scope ofwhich is defined in the claims and their equivalents.

What is claimed is:
 1. An apparatus comprising: a substrate; a firstslab waveguide formed on the substrate; channel waveguides of differinglengths formed on the substrate, light output from the first slabwaveguide being input to the channel waveguides; and a second slabwaveguide formed on the substrate, light output from the channelwaveguides being input to the second slab waveguide, wherein an end faceof the second slab waveguide shares a face with an end face of thesubstrate.
 2. An apparatus as in claim 1, wherein a wavelength divisionmultiplexed (WDM) light is input to the first slab waveguide and, aftertraveling through the first slab waveguide, is input to the channelwaveguides and, after traveling through the channel waveguides, is inputto the second slab waveguide, the channel waveguides having differencesin optical path lengths, respectively, so that angular dispersion isgenerated in lights output from the channel waveguides in accordancewith wavelengths in the WDM light.
 3. An apparatus as in claim 1,wherein output ends of the channel waveguides are arranged on thesubstrate in a straight line.
 4. An apparatus as in claim 1, wherein aboundary between the channel waveguides and the second slab waveguideforms a straight line.
 5. An apparatus as in claim 1, furthercomprising: a focusing device formed inside said second slab waveguideto focus lights output from said second slab waveguide.
 6. An apparatusas in claim 2, wherein the apparatus further comprises: a focusingdevice focusing the angularly dispersed lights at different wavelengthsat different positions, respectively; and a reflecting device at aposition where angular dispersed light at a respective wavelength isfocused.
 7. An apparatus as in claim 2, wherein the apparatus furthercomprises: a focusing device focusing the angularly dispersed lights atdifferent wavelengths at different positions, respectively; and areflecting surface at a position where angular dispersed light at arespective wavelength is focused, the reflecting surface beingelectronically tiltable to affect a position at which wavelengths in achannel corresponding to said respective wavelength are incident on thereflecting surface.
 8. An apparatus as in claim 2, wherein the apparatusfurther comprises: a focusing device focusing the angularly dispersedlights at different wavelengths at different positions, respectively;and a photoelectric converter at a position where angular dispersedlight at a respective wavelength is focused.
 9. An apparatus as in claim2, further comprising: a focusing device formed in the second slabwaveguide, the focusing device focusing the angularly dispersed lightsat different wavelengths at different positions, respectively.
 10. Anapparatus as in claim 9, further comprising: a reflecting device at aposition where angular dispersed light at a respective wavelength isfocused.
 11. An apparatus as in claim 9, further comprising: areflecting surface at a position where angular dispersed light at arespective wavelength is focused, the reflecting surface beingelectronically tiltable to affect a position at which wavelengths in achannel corresponding to said respective wavelength are incident on thereflecting surface.
 12. An apparatus as in claim 9, further comprising:a photoelectric converter at a position where angular dispersed light ata respective wavelength is focused.
 13. An apparatus comprising: asubstrate; a slab waveguide formed on the substrate; channel waveguidesof differing lengths formed on the substrate, light input to the slabwaveguide traveling through the slab waveguide and then being input tothe channel waveguides, wherein a wavelength division multiplexed (WDM)light is input to the slab waveguide to thereby travel through the slabwaveguide and be input to the channel waveguides of differing lengths,the channel waveguides of differing lengths having differences inoptical path lengths, respectively, so that light at differentwavelengths in the WDM light is angularly dispersed from an end face ofthe substrate in different directions, respectively, in accordance withwavelength; and a focusing device focusing the angularly dispersedlights at different wavelengths at different positions, respectively.14. An apparatus as in claim 13, wherein the apparatus furthercomprises: a reflecting device at a position where angular dispersedlight at a respective wavelength is focused.
 15. An apparatus as inclaim 13, wherein the apparatus further comprises: a reflecting surfaceat a position where angular dispersed light at a respective wavelengthis focused, the reflecting surface being electronically tiltable toaffect a position at which wavelengths in a channel corresponding tosaid respective wavelength are incident on the reflecting surface. 16.An apparatus as in claim 13, wherein the apparatus further comprises: aphotoelectric converter at a position where angular dispersed light at arespective wavelength is focused.
 17. An apparatus as in claim 13,wherein output ends of the channel waveguides of differing lengths arearranged on the substrate in a straight line.
 18. An apparatuscomprising: a first optical device receiving a first wavelength divisionmultiplexed (WDM) light, comprising a substrate, a slab waveguide formedon the substrate, and channel waveguides of differing lengths formed onthe substrate, wherein the first WDM light is input to the slabwaveguide to thereby travel through the slab waveguide and be input tothe channel waveguides of differing lengths, the channel waveguides ofdiffering lengths having differences in optical path lengths,respectively, so that lights at different wavelengths in the first WDMlight are angularly dispersed from an end face of the substrate indifferent directions, respectively, in accordance with wavelength; asecond optical device receiving a second WDM light, comprising asubstrate, a slab waveguide formed on the substrate, and channelwaveguides of differing lengths formed on the substrate, wherein thesecond WDM light is input to the slab waveguide to thereby travelthrough the slab waveguide and be input to the channel waveguides ofdiffering lengths, the channel waveguides of differing lengths havingdifferences in optical path lengths, respectively, so that lights atdifferent wavelengths in the second WDM light are angularly dispersedfrom an end face of the substrate in different directions, respectively,in accordance with wavelength; at least one focusing device focusing thelights at different wavelengths angularly dispersed from the firstoptical device at different positions, respectively, and focusing thelights at different wavelengths angularly dispersed from the secondoptical device at different positions, respectively, so that angularlydispersed light from the first optical device and angularly dispersedlight from the second optical device at the same wavelength are focusedat the same position; and a reflector positioned at said same positionand controllable to reflect light focused at said same position to thefirst or second optical devices.
 19. An apparatus as in claim 18,wherein said first optical device further comprises an additional slabwaveguide formed on the substrate of the first optical device, lightoutput from the channel waveguides of differing lengths of the firstoptical device being input to said additional slab waveguide of thefirst optical device to thereafter be angularly dispersed from said endface of the substrate of the first optical device; and said secondoptical device further comprises an additional slab waveguide formed onthe substrate of the second optical device, light output from thechannel waveguides of differing lengths of the second optical devicebeing input to said additional slab waveguide of the second opticaldevice to thereafter be angularly dispersed from said end face of thesubstrate of the second optical device.
 20. An apparatus as in claim 18,wherein the substrates of the first and second optical devices are thesame substrate.
 21. An apparatus as in claim 19, wherein the substratesof the first and second optical devices are the same substrate.
 22. Anapparatus as in claim 19, wherein said at least one focusing devicecomprises: a first surface formed in the additional slab waveguide ofthe first optical device, the first surface focusing the lights atdifferent wavelengths angularly dispersed from the first optical deviceat different positions, respectively, and a second surface formed in theadditional slab waveguide of the second optical device, the secondsurface focusing the lights at different wavelengths angularly dispersedfrom the second optical device at different positions, respectively. 23.An apparatus comprising: a first optical device receiving a firstwavelength division multiplexed (WDM) light, comprising a substrate, afirst slab waveguide formed on the substrate, channel waveguides formedon the substrate, light output from the first slab waveguide being inputto the channel waveguides, and a second slab waveguide formed on thesubstrate, light output from the channel waveguides being input to thesecond slab waveguide, an end face of the second slab waveguide sharinga face with an end face of the substrate, the first WDM light beinginput to the first slab waveguide to thereby travel through the firstslab waveguide and thereafter be input to the channel waveguides andthen to the second slab waveguide, the channel waveguides havingdifferences in optical path lengths, respectively, so that angulardispersion is generated in lights output from the channel waveguides inaccordance with wavelengths in the first WDM light; a second opticaldevice receiving a second WDM light, comprising a substrate, a firstslab waveguide formed on the substrate, channel waveguides formed on thesubstrate, light output from the first slab waveguide being input to thechannel waveguides, and a second slab waveguide formed on the substrate,light output from the channel waveguides being input to the second slabwaveguide, an end face of the second slab waveguide sharing a face withan end face of the substrate, the second WDM light being input to thefirst slab waveguide to thereby travel through the first slab waveguideand thereafter be input to the channel waveguides and then to the secondslab waveguide, the channel waveguides having differences in opticalpath lengths, respectively, so that angular dispersion is generated inlights output from the channel waveguides in accordance with wavelengthsin the second WDM light; at least one focusing device focusing lights atdifferent wavelengths angularly dispersed from the first optical deviceat different positions, respectively, and focusing lights at differentwavelengths angularly dispersed from the second optical device atdifferent positions, respectively, so that angularly dispersed lightfrom the first optical device and angularly dispersed light from thesecond optical device at the same wavelength are focused at the sameposition; and a reflector positioned at said same position andcontrollable to reflect light focused at said same position to the firstor second optical devices.
 24. An apparatus as in claim 23, wherein thesubstrates of the first and second optical devices are the samesubstrate.
 25. An apparatus as in claim 23, wherein said at least onefocusing device comprises: a first surface formed in the second slabwaveguide of the first optical device, the first surface focusing thelights at different wavelengths angularly dispersed from the firstoptical device at different positions, respectively, and a secondsurface formed in the second slab waveguide of the second opticaldevice, the second surface focusing the lights at different wavelengthsangularly dispersed from the second optical device at differentpositions, respectively.